37 ошибок верстальщиков. Не делай так!

Привет! Ошибки допускают все, даже опытные верстальщики. И часто эти ошибки не поддаются никакому объяснению - они просто есть. То класс не так написан, то в сафари все поехало…В общем, в этом видео я хотел бы рассмотреть аж 37 подобных случаев, ошибок, которые не нужно допускать.
В этом видео я не смеюсь над теми, кто их совершает, да даже сам некоторые до сих пор совершаю. Я хочу лишь донести то, что это действительно ошибки, и как их исправить. Поехали!

Содержание:
00:00 - Вступление и критерии верстки
01:30 - Названия классов транслитом
02:38 - Названия классов не по назначению
03:44 - Названия классов верные, но теги - нет
04:40 - Большая длина названий классов
05:28 - Большая вложенность классов
06:40 - Проблема именования в БЭМ - элемент элемента
08:08 - Проблема именования в БЭМ - модификаторы
09:08 - Неверная табуляция кода
10:08 - Неправильная семантика в html
11:00 - Большая вложенность в html
12:26 - Неверное использование заголовков
14:22 - Использование тегов там, где их использовать нельзя
15:52 - Неверное использование ссылок и кнопок
17:48 - Декоративные элементы в html
18:48 - Декоративные изображения в html
19:44 - Проблема переполнения на сайте
21:26 - Не соблюдается базовая доступность
21:53 - Кириллица в названиях классов, картинок и т.д.
23:18 - Использование id для стилизации
24:15 - Бездумное использование br
25:36 - Использование инлайн-стилей
26:15 - Неверное использование абсолютного позиционирования
28:02 - Организация отступов в верстке
29:25 - Использование фиксированной высоты
30:35 - Следите за наследованием шрифтов
31:45 - Ошибки в стилизации textarea
33:52 - cursor: pointer и hover для интерактивных элементов
34:38 - Удаление outline без альтернативы
35:46 - Сброс и нормализация стилей
36:29 - Фоновые изображения и фоновый цвет
37:27 - Дробные пиксели
38:14 - анимация через left вместо transform
39:16 - Большое количество медиа-запросов
40:09 - Использование !important
41:22 - Неверный подход к верстке
42:20 - Несоответствие кодстайлу
43:03 - Кроссбраузерность
43:24 - Проблемы адаптива
44:02 - Заключение

Subscribe : https://www.youtube.com/channel/UCxJyCit95jsb-JLE3kXnq1Q

#web-development

What is GEEK

Buddha Community

37 ошибок верстальщиков. Не делай так!

37 ошибок верстальщиков. Не делай так!

Привет! Ошибки допускают все, даже опытные верстальщики. И часто эти ошибки не поддаются никакому объяснению - они просто есть. То класс не так написан, то в сафари все поехало…В общем, в этом видео я хотел бы рассмотреть аж 37 подобных случаев, ошибок, которые не нужно допускать.
В этом видео я не смеюсь над теми, кто их совершает, да даже сам некоторые до сих пор совершаю. Я хочу лишь донести то, что это действительно ошибки, и как их исправить. Поехали!

Содержание:
00:00 - Вступление и критерии верстки
01:30 - Названия классов транслитом
02:38 - Названия классов не по назначению
03:44 - Названия классов верные, но теги - нет
04:40 - Большая длина названий классов
05:28 - Большая вложенность классов
06:40 - Проблема именования в БЭМ - элемент элемента
08:08 - Проблема именования в БЭМ - модификаторы
09:08 - Неверная табуляция кода
10:08 - Неправильная семантика в html
11:00 - Большая вложенность в html
12:26 - Неверное использование заголовков
14:22 - Использование тегов там, где их использовать нельзя
15:52 - Неверное использование ссылок и кнопок
17:48 - Декоративные элементы в html
18:48 - Декоративные изображения в html
19:44 - Проблема переполнения на сайте
21:26 - Не соблюдается базовая доступность
21:53 - Кириллица в названиях классов, картинок и т.д.
23:18 - Использование id для стилизации
24:15 - Бездумное использование br
25:36 - Использование инлайн-стилей
26:15 - Неверное использование абсолютного позиционирования
28:02 - Организация отступов в верстке
29:25 - Использование фиксированной высоты
30:35 - Следите за наследованием шрифтов
31:45 - Ошибки в стилизации textarea
33:52 - cursor: pointer и hover для интерактивных элементов
34:38 - Удаление outline без альтернативы
35:46 - Сброс и нормализация стилей
36:29 - Фоновые изображения и фоновый цвет
37:27 - Дробные пиксели
38:14 - анимация через left вместо transform
39:16 - Большое количество медиа-запросов
40:09 - Использование !important
41:22 - Неверный подход к верстке
42:20 - Несоответствие кодстайлу
43:03 - Кроссбраузерность
43:24 - Проблемы адаптива
44:02 - Заключение

Subscribe : https://www.youtube.com/channel/UCxJyCit95jsb-JLE3kXnq1Q

#web-development

Bukola Ayodele

1642081085

MUTANT MAIL Review — ⚠️Warning⚠️ — IS A SCAM?

Mutant mail Review

Game changer Email Management Solution for Individuals, Small Business owners, Hustlers & Entrepreneurs.

On this page, I have covered each & every aspect of this New-To-Market Product Mutant mail, so that you can make an informed purchase decision easily.

Note: i have huge bonuses for you below if you buy using my link more detail below

With Privacy-Focused  Email management Solution

Do You Want to Simplify your Email management?

Your Chance to Cash & Grow.

Now Send, Reply and Receive all your Domain's emails through one Mailbox of your Choice.

What Is Mutant mail?

Mutant Mail Allows to Reply, Receive and Send all Domain's emails from single Mailbox (Gmail, Hotmail, Yahoo anything).

The only Server Side Solution.

How do you reply to email that you get on your domain? (admin@domain, support@domain, legal@domain etc.)

With MutantMail you can get all those domains on your Gmail/Hotmail/Yahoo, whichever you choose and just reply.

And it all goes using your domain's email id. So effectively, your all emails are flowing into one Inbox and still maintaining your alias cover

Mutant Mail Recieve, Send, Reply from Single Inbox

What does that benefit.

Easy Email maintenance. Not joking. Every domain needs at-least five email ids (webmaster, legal, support, admin, contact). Imagine if you have 5 domains. That's 25 email ids.

Faster email response. No more logging into individual email ids anymore. No more headache of remember passwords. Just reply and Mutant Mail will take care of sending it via your domain.

No need to pay for email hosting. No need to put 25 email ids in one email client. Anything your inbox support (including client), Mutant Mail supports.
This kind of solution comes once in a long time. That's actually never been done before.

 

How It Works

Step #1 Sign on Mutant Mail

Every good thing starts with registration and Mutant Mail has adopted everything great.

Our Sign up is the fastest out there and requires only 3 fields, to keep everything privacy-related in check.

Mutant Mail Register

Mutant Mail Email Aliases

 

Step #2  Add your Domain

Just go to the "Your domains" tab, and follow the two-step process.

It requires copy and pasting a few lines.

The process will attach your domain's email through Mutant Mail gateway to receive, send and reply to emails from a single mailbox.

 

Step #3  Finally the email

Generate Email ID either on the fly or generate beforehand.

If the catch-all is enabled, we'll automatically create the alias in your dashboard as soon as it receives its first email.

You can reply to these and send a new email, from the convenience of your inbox, while maintaining your alias persona!

 

                                                                               👉⚠️Click Here To Get Mutant mail And Custom Bonuses⚠️👈
 

Mutant mail Review OVERVIEW

VendorFresent LLC
ProductMutant mail
Launch Date2022-Jan-15
Launch Time12:00 EST
Front-End Price$72
Official Site>> Click Here <<
RefundYES, 30 Days Money-Back Guarantee
NicheSoftware
SupportEffective Response
Bonuses>> Huge Bonuses Check Below <<
RecommendedHighly Recommended
Skill Level NeededAll Levels

Mutant mail Review – Features and Benefits

Single Inbox for your domains

We have a lovely interface, but You don't need to login into our system to reply, receive or send email through your domain email id.

To reply to any email received on your forwarded email (eg on Gmail) all you need to do is click on reply, and your recipient will get an email from your domain's email id.

This is great if you want to keep your alias appearance and also the convenience of your current email provider.

 

Complete Encryption

Bring your own GPG/OpenPGP public keys and add them per recipient.

You can then easily toggle encryption on and off. With encryption on, all forwarded messages will be encrypted with your public key. Only you will be able to decrypt them with the corresponding private key.

This is great if you are using Gmail or Outlook and wish to prevent any inbox snooping.

Control Your Alias

Attach your Domain and use it for email e.g. alias@example.com.

MutantMail allows you to enable or disable the catch-all functionality for each of your domains.

You can then manage your aliases and deactivate/delete any that start receiving spam!

Additionally, rules can be created to block specific sender

Multiple Recipients

If you'd like an alias to go to more than one recipient you can easily add multiple recipients from your dashboard.

Certainly useful, when you are at work email but don't want to miss out emails on important alias.

Multiple Recipients

Reply to and Send from

Email ID segregation

In case you want to segregate your email ids, across your domains. For example, all support@anydomain should go to one email id, and all legal@anydomain goto other, it's very easy to implement.

Our customers are doing it to segregate their operation, support emails from admin and legal emails.

API Access

Manage your aliases, recipients, domains and additional usernames using the MutantMail API.

In order to use the API you first need to generate an API access token in your account settings.

Mutant Mail API

Mutant Mail Blend In Crowd

Anonymity and Privacy

We absolutely would hate our emails to be snooped on. So, we have ensured same for our customers.

We do not store, log or track any email content. Only thing we log is size of email, without tracking where it came from and for whom.

Additional security like Two-factor authentication and PGP encryption can be used at will.

 👉⚠️Click Here To Get Mutant mail And Custom Bonuses⚠️👈

Mutant mail REVIEW – Why choose Mutant Mail?

For making email management easy.

Mutant Mail maintains your alias, whenever you hit reply in your mailbox, and ensures the receiver gets an email from your correct alias, instead of your current mailbox.

So, effectively you can send, reply and receive to/from info@example1.com, help@example2.com, webmaster@example3.com using any inbox of your choice.

Skip, login to every email id daily with us.

Mutant Mail Recieve, Send, Reply from Single Inbox

The benefit starts with a single domain.

Each domain minimum needs five email alias (admin, help, legal, support, webmaster).

It's a hustle to log in to each one daily and reply, making sure none of the important emails are delayed.

Just imagine having five domains. That's 25 email id.

Better than Email forwarder/Client.

Email clients are a mess as the email id counts go higher. Forget 25 and try adding 10 to an email client.

Email clients cannot be used remotely in case your laptop is not handy.

Then, of course, you need to choose from the drop-down every time you reply to an email, to maintain an appearance.

Email forwarders are awesome, but you cannot reply through them, as they will not maintain your business email id alias.

Mutant Mail Email Forwarding

Mutant Mail Email Id Segregation

For Email IDs Segregation.

Let's say you run multiple businesses, and you want to segregate email id across multiple domains into groups.

With Mutant Mail, every email id could be configured for a different destination email. That mean, all support emails can go to the email your support team manages, or all legal email can go to the email your legal team handle, and so on. Segregating your email id types across the business.

And do not worry, each of the forwarded emails can be replied to easily while maintaining the alias appearance it was sent on.

 👉⚠️Click Here To Get Mutant mail And Custom Bonuses⚠️👈

Here is What People Say About This Product

"You wont know you you managed with Mutantmail Mutantmail is one of those product that come up rare and saves you loads of time. If like me you have lots of domains that you manage with all their associated email accounts having to be monitored from lots of different mailboxes. Imagine being able to monitor and reply to all these emails from one nominated email account from this point forward :-)." 


 

"Brilliant Product and Essential Tool This a WOW product, just pure brilliance and clean execution. I've had my fair share of domain email pains and I don't even have that many active in use domains. Mutant mail makes creating IDs, forwarding emails, replying using your own domain named emails a breeze. Top top it off, minimalistic UI that is fast and just works like a dream; and a founder that is passionate about his creation and customers' success. Alex spent generous time on Zoom and answered like 10 questions from me. When Mutant mail is paired with DoneDone or Flowlu, the friction along the email communication/support process for the business is radically reduced to almost nothing. Plus, it really builds up your organizations image - professional and streamlined inquiry/communication handling. Highest recommendation!" 


 

"Outstanding product and superb customer support This product is a hidden gem in my opinion. I think it's going to save me money relatively quickly. More importantly, the founder Abhishak, is simply superb. He is very involved and will bend over backwards so that you get what you need from the product. In a matter of a few days, he has done 3 zoom calls with me, helping me configure things and iron out any teething issues. I genuinely hope this succeeds, we want more founders like this - who care about their product and their customers - if you get that right the dollars will follow." 


 

"Huge Time Saver Definitely a very useful product and will save me a lot of time. I build and manage many sites, so managing emails for all those sites is a pain. It's not just setting up the sites, but also setting up all the various email accounts. This has saved me a lot of time in setting up multiple email accounts and logging into multiple email accounts just to reply from a specific support@ sales@ john@ partners@ etc@ email address. If you pay per user for your emails, but have one person covering multiple "users," then this is a must-have. It took me a bit to set up as I ran into issues that were not related to mutant mail. But when I asked a question to the mutant team, they jumped on Skype with me to resolve just in case it was an issue with their platform (which it wasn't)." 

 👉⚠️Click Here To Get Mutant mail And Custom Bonuses⚠️👈

Price and Evaluation

PLAN DETAIL

 50 Email IDs

 10 Domains Allowed

 15 Recipient Email IDs

 Paid Plan Settings

 Option to disable catch-all

 Additional Alias Domains

 Priority Email Queue

 5 GB Monthly Bandwidth

 View Failed Deliveries

$5.99 / Month

Billed Yearly

 

Conclusion

I hope that my Mutant mail review can assist you in making a more informed and timely decision. If you have any questions, please leave them in the comments section of this blog post. Thank you for your time. Best of luck to you!

JUST 2 SIMPLE STEPS TO GET THESE HUGE BONUSES BELOW

  1.  
    1. Get Mutant mail by Clicking here to Get it now or via any link on this page
       
    2. Your bonuses will be delivered inside your JVZoo Purchases Dashboard, Warriorplus, etc. If you cannot find them, forward the receipt to my email  at: steveseun[@]gmail.com . I’ll help you out.

 

 

Click Here to Get Mutant mail Sites And Bonuses Listed Below

Bonus #1: Profit Store Pro

Profit_Store_Pro

With Profit Store Pro you’ll be one of the 1st people outside of my mastermind to have a proven step-by-step guide on how to set up your own eCommerce stores… and then, Use Never-Before-Revealed Tactics To Quickly Monetize Your Stores With FB Ads. Profit Store Pro will set you on the road to BIG profits…

Bonus #2: eCom Finder

ecom-Finder

Hate doing research? So do I! This application is going to solve all your product research needs by uncovering the hottest, most PROFITABLE products to put in your stores. And it’s yours

 

Bonus #3: The Newbies Guide To Becoming A Successful Dropshipper

Newbies_Guide_Successful_Dropshipper_smaller

Bonus #4: 110 Niches For ECommerce

Screen-Shot-2015-10-15-at-15.02.09

You’ll discover the most profitable sought after niches to sell on shopfiy right now. Don’t waste time in niches that will never turn a ROI for you. Start cashing in for real, right from the get go!

Bonus #5: eCommerce Riches

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Bonus #6: eCommerce Arbitrage

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Bonus #7: 8 Ways To Increase Your eCommerce Average Order

shippingthreshold-Target

 

Bonus #8: Holiday Goldmine

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Bonus #9: Product Type You Can Sell

ecommerce-products-smallGet a head start, with this informative guide that lists all the types of products that are selling and in demand.

Bonus #10: 21 Tips To Make Your eCommerce Homepage a Conversion Magnet

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Bonus #11: Winning The Wholesale & Dropshipping Game

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How to find your own wholesale suppliers.

Bonus #12: Physical Product Profits

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Fastest Way To Sell Physical Products Through Amazon!

BONUS #13: ULTIMATE EBAY GUIDE 

In this guide to drop shipping on eBay you will learn everything you need to know from how to get started to selling like a Pro. You will learn all of the best Chinese Drop Shipping websites that all the big sellers are using, including examples of products that will make you hundreds of dollars at a time. You will also learn the best way to list your items, telling one of the biggest tips no other guide will ever tell you.

BONUS #14: 11 RETARGETING HACKS

Bonus #15: WP Store Press

Bonus5

WP Store Press is a WordPress theme that will allow you to easily create your own shopping mall within Facebook. This WordPress theme has been designed to allow e-commerce marketers to have Facebook, mobile, and pc based e-commerce stores up and running in as little as five minutes. This is perfect for anyone who is wanting to tap into the power of Facebook to sell our products.

Bonus #16: Instagram Traffic

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For the first time ever… You’ll learn how to use Instagram to create a viral buzz for your products that are people who are going to go crazy for… See Instagram followers differ to Facebook users, since we will see every single post you write, bringing in traffic, and when you master a few golden never before seen secrets, you’ll be MILES AHEAD of the competition

Bonus #17: Pinterest Perfection

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Bonus #18: Finally Drive Huge Traffic from Facebook and Profit!

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Finally Drive Huge Traffic from Facebook and Profit!

BONUS #19: PASSIVE EMAIL RICHES

Learn how you can achieve 50% open rates & 30% click rates from all your emails.

Bonus #20: Low Cost web Traffic Surge

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Bonus #21: The Traffic Generation Personality Type

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Bonus #22: Lead Avalanche

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Bonus #23: Traffic Extreme

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Bonus #24: Instant Traffic Mastery

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Bonus #25: Like, Share & Follow

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Here’s Your 30 Day Guide To Mastering Social Media Marketing! Learn How To Use Social Media More Efficiently And Increase Your Outreach With Specific, Proven Strategies!
What is social media? Now, most of us are aware of some of the most popular social media sites but what are we? The term “social media” is basically the method of how people interact, share, and create information over a virtual network and community.

Bonus #26: Quick Guide To WordPress SEO

seo-guide

BONUS #27: GRAPHICS BLACKBOX

Grab your graphics design solution and shortcut.
367 brand new and original graphics for your website.
For a total of 20 modules

Bonus #28: WP Easy Optin Pro Plugin

b11

The easiest way to add email blocks to any blog page in your wordpress theme.
An effective way to increase your mailing list through blog posts.

Bonus #29: SEO Stone Plugin

seostone

 

 

Bonus #30: Reputation Management

reputation-management

Bonus #31: Video Support Force

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Discover How You Can Quickly and Easily Create Video Training Centers For Your Products…That Will Lower Support Tickets, Lower Refund Rates, Create High Stick Rates, And Let You Run Your Business On Autopilot!

Bonus #32: Ultimate Minisite Templates

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Bonus #33: 30 Stunning Graphical Images For website

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4% more total views on average are attracted by content containing compelling images than content without images. The better and clearer the images, the higher the consumer base!

Bonus #34: Social Signals for SEO

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Bonus #35: 50+ Niche Pack

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Bonus #36: Wp Local Business Plugin

Wp-Local-Business-Plugin

An Easy To Use System That Creates Social-Powered Business Landing Pages In Seconds! Everything You Need To Setup A Killer Professional Business Landing Page That Anyone Can Create! This system is designed for anyone who wants to get a full business landing page site up and running in minutes without installing a big bulky

Bonus #37: WP VIDEO OPTIN

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Bonus #38: Youtube Video Mastery

5

Learn how to use YouTube to earn passive income, monetize your videos & most importantly create compelling video content specifically for your YouTube videos.

Bonus #39: Tube Ads Genie

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Literally Force Visitors Who Watch Videos On Your Site To Click on YOUR ADS Bringing You Commissions & Sales On Complete AUTOPILOT

Bonus #40: Video Marketing Hack

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Bonus #41: Uber Optin plugin

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Bonus #42: Membership Income Course

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Bonus #43: WP Members Pro

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Bonus #44: Interview with membership expert Dennis Becker

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Bonus #45: Social boost plugin

social-boost

Bonus #46: Wp EZ Share It Plugin

Wp-EZ-Share-It-Plugin

New Powerful, Off-The-Grid WP Plugin Allows Users To Share Your Images And Videos Of Your Blog And Link Them Back To You…Generating A Tsunami Of Traffic To YOUR Blog!

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Swift Tips: A Collection Useful Tips for The Swift Language

SwiftTips

The following is a collection of tips I find to be useful when working with the Swift language. More content is available on my Twitter account!

Property Wrappers as Debugging Tools

Property Wrappers allow developers to wrap properties with specific behaviors, that will be seamlessly triggered whenever the properties are accessed.

While their primary use case is to implement business logic within our apps, it's also possible to use Property Wrappers as debugging tools!

For example, we could build a wrapper called @History, that would be added to a property while debugging and would keep track of all the values set to this property.

import Foundation

@propertyWrapper
struct History<Value> {
    private var value: Value
    private(set) var history: [Value] = []

    init(wrappedValue: Value) {
        self.value = wrappedValue
    }
    
    var wrappedValue: Value {
        get { value }

        set {
            history.append(value)
            value = newValue
        }
    }
    
    var projectedValue: Self {
        return self
    }
}

// We can then decorate our business code
// with the `@History` wrapper
struct User {
    @History var name: String = ""
}

var user = User()

// All the existing call sites will still
// compile, without the need for any change
user.name = "John"
user.name = "Jane"

// But now we can also access an history of
// all the previous values!
user.$name.history // ["", "John"]

Localization through String interpolation

Swift 5 gave us the possibility to define our own custom String interpolation methods.

This feature can be used to power many use cases, but there is one that is guaranteed to make sense in most projects: localizing user-facing strings.

import Foundation

extension String.StringInterpolation {
    mutating func appendInterpolation(localized key: String, _ args: CVarArg...) {
        let localized = String(format: NSLocalizedString(key, comment: ""), arguments: args)
        appendLiteral(localized)
    }
}


/*
 Let's assume that this is the content of our Localizable.strings:
 
 "welcome.screen.greetings" = "Hello %@!";
 */

let userName = "John"
print("\(localized: "welcome.screen.greetings", userName)") // Hello John!

Implementing pseudo-inheritance between structs

If you’ve always wanted to use some kind of inheritance mechanism for your structs, Swift 5.1 is going to make you very happy!

Using the new KeyPath-based dynamic member lookup, you can implement some pseudo-inheritance, where a type inherits the API of another one 🎉

(However, be careful, I’m definitely not advocating inheritance as a go-to solution 🙃)

import Foundation

protocol Inherits {
    associatedtype SuperType
    
    var `super`: SuperType { get }
}

extension Inherits {
    subscript<T>(dynamicMember keyPath: KeyPath<SuperType, T>) -> T {
        return self.`super`[keyPath: keyPath]
    }
}

struct Person {
    let name: String
}

@dynamicMemberLookup
struct User: Inherits {
    let `super`: Person
    
    let login: String
    let password: String
}

let user = User(super: Person(name: "John Appleseed"), login: "Johnny", password: "1234")

user.name // "John Appleseed"
user.login // "Johnny"

Composing NSAttributedString through a Function Builder

Swift 5.1 introduced Function Builders: a great tool for building custom DSL syntaxes, like SwiftUI. However, one doesn't need to be building a full-fledged DSL in order to leverage them.

For example, it's possible to write a simple Function Builder, whose job will be to compose together individual instances of NSAttributedString through a nicer syntax than the standard API.

import UIKit

@_functionBuilder
class NSAttributedStringBuilder {
    static func buildBlock(_ components: NSAttributedString...) -> NSAttributedString {
        let result = NSMutableAttributedString(string: "")
        
        return components.reduce(into: result) { (result, current) in result.append(current) }
    }
}

extension NSAttributedString {
    class func composing(@NSAttributedStringBuilder _ parts: () -> NSAttributedString) -> NSAttributedString {
        return parts()
    }
}

let result = NSAttributedString.composing {
    NSAttributedString(string: "Hello",
                       attributes: [.font: UIFont.systemFont(ofSize: 24),
                                    .foregroundColor: UIColor.red])
    NSAttributedString(string: " world!",
                       attributes: [.font: UIFont.systemFont(ofSize: 20),
                                    .foregroundColor: UIColor.orange])
}

Using switch and if as expressions

Contrary to other languages, like Kotlin, Swift does not allow switch and if to be used as expressions. Meaning that the following code is not valid Swift:

let constant = if condition {
                  someValue
               } else {
                  someOtherValue
               }

A common solution to this problem is to wrap the if or switch statement within a closure, that will then be immediately called. While this approach does manage to achieve the desired goal, it makes for a rather poor syntax.

To avoid the ugly trailing () and improve on the readability, you can define a resultOf function, that will serve the exact same purpose, in a more elegant way.

import Foundation

func resultOf<T>(_ code: () -> T) -> T {
    return code()
}

let randomInt = Int.random(in: 0...3)

let spelledOut: String = resultOf {
    switch randomInt {
    case 0:
        return "Zero"
    case 1:
        return "One"
    case 2:
        return "Two"
    case 3:
        return "Three"
    default:
        return "Out of range"
    }
}

print(spelledOut)

Avoiding double negatives within guard statements

A guard statement is a very convenient way for the developer to assert that a condition is met, in order for the execution of the program to keep going.

However, since the body of a guard statement is meant to be executed when the condition evaluates to false, the use of the negation (!) operator within the condition of a guard statement can make the code hard to read, as it becomes a double negative.

A nice trick to avoid such double negatives is to encapsulate the use of the ! operator within a new property or function, whose name does not include a negative.

import Foundation

extension Collection {
    var hasElements: Bool {
        return !isEmpty
    }
}

let array = Bool.random() ? [1, 2, 3] : []

guard array.hasElements else { fatalError("array was empty") }

print(array)

Defining a custom init without loosing the compiler-generated one

It's common knowledge for Swift developers that, when you define a struct, the compiler is going to automatically generate a memberwise init for you. That is, unless you also define an init of your own. Because then, the compiler won't generate any memberwise init.

Yet, there are many instances where we might enjoy the opportunity to get both. As it turns out, this goal is quite easy to achieve: you just need to define your own init in an extension rather than inside the type definition itself.

import Foundation

struct Point {
    let x: Int
    let y: Int
}

extension Point {
    init() {
        x = 0
        y = 0
    }
}

let usingDefaultInit = Point(x: 4, y: 3)
let usingCustomInit = Point()

Implementing a namespace through an empty enum

Swift does not really have an out-of-the-box support of namespaces. One could argue that a Swift module can be seen as a namespace, but creating a dedicated Framework for this sole purpose can legitimately be regarded as overkill.

Some developers have taken the habit to use a struct which only contains static fields to implement a namespace. While this does the job, it requires us to remember to implement an empty private init(), because it wouldn't make sense for such a struct to be instantiated.

It's actually possible to take this approach one step further, by replacing the struct with an enum. While it might seem weird to have an enum with no case, it's actually a very idiomatic way to declare a type that cannot be instantiated.

import Foundation

enum NumberFormatterProvider {
    static var currencyFormatter: NumberFormatter {
        let formatter = NumberFormatter()
        formatter.numberStyle = .currency
        formatter.roundingIncrement = 0.01
        return formatter
    }
    
    static var decimalFormatter: NumberFormatter {
        let formatter = NumberFormatter()
        formatter.numberStyle = .decimal
        formatter.decimalSeparator = ","
        return formatter
    }
}

NumberFormatterProvider() // ❌ impossible to instantiate by mistake

NumberFormatterProvider.currencyFormatter.string(from: 2.456) // $2.46
NumberFormatterProvider.decimalFormatter.string(from: 2.456) // 2,456

Using Never to represent impossible code paths

Never is quite a peculiar type in the Swift Standard Library: it is defined as an empty enum enum Never { }.

While this might seem odd at first glance, it actually yields a very interesting property: it makes it a type that cannot be constructed (i.e. it possesses no instances).

This way, Never can be used as a generic parameter to let the compiler know that a particular feature will not be used.

import Foundation

enum Result<Value, Error> {
    case success(value: Value)
    case failure(error: Error)
}

func willAlwaysSucceed(_ completion: @escaping ((Result<String, Never>) -> Void)) {
    completion(.success(value: "Call was successful"))
}

willAlwaysSucceed( { result in
    switch result {
    case .success(let value):
        print(value)
    // the compiler knows that the `failure` case cannot happen
    // so it doesn't require us to handle it.
    }
})

Providing a default value to a Decodable enum

Swift's Codable framework does a great job at seamlessly decoding entities from a JSON stream. However, when we integrate web-services, we are sometimes left to deal with JSONs that require behaviors that Codable does not provide out-of-the-box.

For instance, we might have a string-based or integer-based enum, and be required to set it to a default value when the data found in the JSON does not match any of its cases.

We might be tempted to implement this via an extensive switch statement over all the possible cases, but there is a much shorter alternative through the initializer init?(rawValue:):

import Foundation

enum State: String, Decodable {
    case active
    case inactive
    case undefined
    
    init(from decoder: Decoder) throws {
        let container = try decoder.singleValueContainer()
        let decodedString = try container.decode(String.self)
        
        self = State(rawValue: decodedString) ?? .undefined
    }
}

let data = """
["active", "inactive", "foo"]
""".data(using: .utf8)!

let decoded = try! JSONDecoder().decode([State].self, from: data)

print(decoded) // [State.active, State.inactive, State.undefined]

Another lightweight dependency injection through default values for function parameters

Dependency injection boils down to a simple idea: when an object requires a dependency, it shouldn't create it by itself, but instead it should be given a function that does it for him.

Now the great thing with Swift is that, not only can a function take another function as a parameter, but that parameter can also be given a default value.

When you combine both those features, you can end up with a dependency injection pattern that is both lightweight on boilerplate, but also type safe.

import Foundation

protocol Service {
    func call() -> String
}

class ProductionService: Service {
    func call() -> String {
        return "This is the production"
    }
}

class MockService: Service {
    func call() -> String {
        return "This is a mock"
    }
}

typealias Provider<T> = () -> T

class Controller {
    
    let service: Service
    
    init(serviceProvider: Provider<Service> = { return ProductionService() }) {
        self.service = serviceProvider()
    }
    
    func work() {
        print(service.call())
    }
}

let productionController = Controller()
productionController.work() // prints "This is the production"

let mockedController = Controller(serviceProvider: { return MockService() })
mockedController.work() // prints "This is a mock"

Lightweight dependency injection through protocol-oriented programming

Singletons are pretty bad. They make your architecture rigid and tightly coupled, which then results in your code being hard to test and refactor. Instead of using singletons, your code should rely on dependency injection, which is a much more architecturally sound approach.

But singletons are so easy to use, and dependency injection requires us to do extra-work. So maybe, for simple situations, we could find an in-between solution?

One possible solution is to rely on one of Swift's most know features: protocol-oriented programming. Using a protocol, we declare and access our dependency. We then store it in a private singleton, and perform the injection through an extension of said protocol.

This way, our code will indeed be decoupled from its dependency, while at the same time keeping the boilerplate to a minimum.

import Foundation

protocol Formatting {
    var formatter: NumberFormatter { get }
}

private let sharedFormatter: NumberFormatter = {
    let sharedFormatter = NumberFormatter()
    sharedFormatter.numberStyle = .currency
    return sharedFormatter
}()

extension Formatting {
    var formatter: NumberFormatter { return sharedFormatter }
}

class ViewModel: Formatting {
    var displayableAmount: String?
    
    func updateDisplay(to amount: Double) {
        displayableAmount = formatter.string(for: amount)
    }
}

let viewModel = ViewModel()

viewModel.updateDisplay(to: 42000.45)
viewModel.displayableAmount // "$42,000.45"

Getting rid of overabundant [weak self] and guard

Callbacks are a part of almost all iOS apps, and as frameworks such as RxSwift keep gaining in popularity, they become ever more present in our codebase.

Seasoned Swift developers are aware of the potential memory leaks that @escaping callbacks can produce, so they make real sure to always use [weak self], whenever they need to use self inside such a context. And when they need to have self be non-optional, they then add a guard statement along.

Consequently, this syntax of a [weak self] followed by a guard rapidly tends to appear everywhere in the codebase. The good thing is that, through a little protocol-oriented trick, it's actually possible to get rid of this tedious syntax, without loosing any of its benefits!

import Foundation
import PlaygroundSupport

PlaygroundPage.current.needsIndefiniteExecution = true

protocol Weakifiable: class { }

extension Weakifiable {
    func weakify(_ code: @escaping (Self) -> Void) -> () -> Void {
        return { [weak self] in
            guard let self = self else { return }
            
            code(self)
        }
    }
    
    func weakify<T>(_ code: @escaping (T, Self) -> Void) -> (T) -> Void {
        return { [weak self] arg in
            guard let self = self else { return }
            
            code(arg, self)
        }
    }
}

extension NSObject: Weakifiable { }

class Producer: NSObject {
    
    deinit {
        print("deinit Producer")
    }
    
    private var handler: (Int) -> Void = { _ in }
    
    func register(handler: @escaping (Int) -> Void) {
        self.handler = handler
        
        DispatchQueue.main.asyncAfter(deadline: .now() + 1.0, execute: { self.handler(42) })
    }
}

class Consumer: NSObject {
    
    deinit {
        print("deinit Consumer")
    }
    
    let producer = Producer()
    
    func consume() {
        producer.register(handler: weakify { result, strongSelf in
            strongSelf.handle(result)
        })
    }
    
    private func handle(_ result: Int) {
        print("🎉 \(result)")
    }
}

var consumer: Consumer? = Consumer()

consumer?.consume()

DispatchQueue.main.asyncAfter(deadline: .now() + 2.0, execute: { consumer = nil })

// This code prints:
// 🎉 42
// deinit Consumer
// deinit Producer

Solving callback hell with function composition

Asynchronous functions are a big part of iOS APIs, and most developers are familiar with the challenge they pose when one needs to sequentially call several asynchronous APIs.

This often results in callbacks being nested into one another, a predicament often referred to as callback hell.

Many third-party frameworks are able to tackle this issue, for instance RxSwift or PromiseKit. Yet, for simple instances of the problem, there is no need to use such big guns, as it can actually be solved with simple function composition.

import Foundation

typealias CompletionHandler<Result> = (Result?, Error?) -> Void

infix operator ~>: MultiplicationPrecedence

func ~> <T, U>(_ first: @escaping (CompletionHandler<T>) -> Void, _ second: @escaping (T, CompletionHandler<U>) -> Void) -> (CompletionHandler<U>) -> Void {
    return { completion in
        first({ firstResult, error in
            guard let firstResult = firstResult else { completion(nil, error); return }
            
            second(firstResult, { (secondResult, error) in
                completion(secondResult, error)
            })
        })
    }
}

func ~> <T, U>(_ first: @escaping (CompletionHandler<T>) -> Void, _ transform: @escaping (T) -> U) -> (CompletionHandler<U>) -> Void {
    return { completion in
        first({ result, error in
            guard let result = result else { completion(nil, error); return }
            
            completion(transform(result), nil)
        })
    }
}

func service1(_ completionHandler: CompletionHandler<Int>) {
    completionHandler(42, nil)
}

func service2(arg: String, _ completionHandler: CompletionHandler<String>) {
    completionHandler("🎉 \(arg)", nil)
}

let chainedServices = service1
    ~> { int in return String(int / 2) }
    ~> service2

chainedServices({ result, _ in
    guard let result = result else { return }
    
    print(result) // Prints: 🎉 21
})

Transform an asynchronous function into a synchronous one

Asynchronous functions are a great way to deal with future events without blocking a thread. Yet, there are times where we would like them to behave in exactly such a blocking way.

Think about writing unit tests and using mocked network calls. You will need to add complexity to your test in order to deal with asynchronous functions, whereas synchronous ones would be much easier to manage.

Thanks to Swift proficiency in the functional paradigm, it is possible to write a function whose job is to take an asynchronous function and transform it into a synchronous one.

import Foundation

func makeSynchrone<A, B>(_ asyncFunction: @escaping (A, (B) -> Void) -> Void) -> (A) -> B {
    return { arg in
        let lock = NSRecursiveLock()
        
        var result: B? = nil
        
        asyncFunction(arg) {
            result = $0
            lock.unlock()
        }
        
        lock.lock()
        
        return result!
    }
}

func myAsyncFunction(arg: Int, completionHandler: (String) -> Void) {
    completionHandler("🎉 \(arg)")
}

let syncFunction = makeSynchrone(myAsyncFunction)

print(syncFunction(42)) // prints 🎉 42

Using KeyPaths instead of closures

Closures are a great way to interact with generic APIs, for instance APIs that allow to manipulate data structures through the use of generic functions, such as filter() or sorted().

The annoying part is that closures tend to clutter your code with many instances of {, } and $0, which can quickly undermine its readably.

A nice alternative for a cleaner syntax is to use a KeyPath instead of a closure, along with an operator that will deal with transforming the provided KeyPath in a closure.

import Foundation

prefix operator ^

prefix func ^ <Element, Attribute>(_ keyPath: KeyPath<Element, Attribute>) -> (Element) -> Attribute {
    return { element in element[keyPath: keyPath] }
}

struct MyData {
    let int: Int
    let string: String
}

let data = [MyData(int: 2, string: "Foo"), MyData(int: 4, string: "Bar")]

data.map(^\.int) // [2, 4]
data.map(^\.string) // ["Foo", "Bar"]

Bringing some type-safety to a userInfo Dictionary

Many iOS APIs still rely on a userInfo Dictionary to handle use-case specific data. This Dictionary usually stores untyped values, and is declared as follows: [String: Any] (or sometimes [AnyHashable: Any].

Retrieving data from such a structure will involve some conditional casting (via the as? operator), which is prone to both errors and repetitions. Yet, by introducing a custom subscript, it's possible to encapsulate all the tedious logic, and end-up with an easier and more robust API.

import Foundation

typealias TypedUserInfoKey<T> = (key: String, type: T.Type)

extension Dictionary where Key == String, Value == Any {
    subscript<T>(_ typedKey: TypedUserInfoKey<T>) -> T? {
        return self[typedKey.key] as? T
    }
}

let userInfo: [String : Any] = ["Foo": 4, "Bar": "forty-two"]

let integerTypedKey = TypedUserInfoKey(key: "Foo", type: Int.self)
let intValue = userInfo[integerTypedKey] // returns 4
type(of: intValue) // returns Int?

let stringTypedKey = TypedUserInfoKey(key: "Bar", type: String.self)
let stringValue = userInfo[stringTypedKey] // returns "forty-two"
type(of: stringValue) // returns String?

Lightweight data-binding for an MVVM implementation

MVVM is a great pattern to separate business logic from presentation logic. The main challenge to make it work, is to define a mechanism for the presentation layer to be notified of model updates.

RxSwift is a perfect choice to solve such a problem. Yet, some developers don't feel confortable with leveraging a third-party library for such a central part of their architecture.

For those situation, it's possible to define a lightweight Variable type, that will make the MVVM pattern very easy to use!

import Foundation

class Variable<Value> {
    var value: Value {
        didSet {
            onUpdate?(value)
        }
    }
    
    var onUpdate: ((Value) -> Void)? {
        didSet {
            onUpdate?(value)
        }
    }
    
    init(_ value: Value, _ onUpdate: ((Value) -> Void)? = nil) {
        self.value = value
        self.onUpdate = onUpdate
        self.onUpdate?(value)
    }
}

let variable: Variable<String?> = Variable(nil)

variable.onUpdate = { data in
    if let data = data {
        print(data)
    }
}

variable.value = "Foo"
variable.value = "Bar"

// prints:
// Foo
// Bar

Using typealias to its fullest

The keyword typealias allows developers to give a new name to an already existing type. For instance, Swift defines Void as a typealias of (), the empty tuple.

But a less known feature of this mechanism is that it allows to assign concrete types for generic parameters, or to rename them. This can help make the semantics of generic types much clearer, when used in specific use cases.

import Foundation

enum Either<Left, Right> {
    case left(Left)
    case right(Right)
}

typealias Result<Value> = Either<Value, Error>

typealias IntOrString = Either<Int, String>

Writing an interruptible overload of forEach

Iterating through objects via the forEach(_:) method is a great alternative to the classic for loop, as it allows our code to be completely oblivious of the iteration logic. One limitation, however, is that forEach(_:) does not allow to stop the iteration midway.

Taking inspiration from the Objective-C implementation, we can write an overload that will allow the developer to stop the iteration, if needed.

import Foundation

extension Sequence {
    func forEach(_ body: (Element, _ stop: inout Bool) throws -> Void) rethrows {
        var stop = false
        for element in self {
            try body(element, &stop)
            
            if stop {
                return
            }
        }
    }
}

["Foo", "Bar", "FooBar"].forEach { element, stop in
    print(element)
    stop = (element == "Bar")
}

// Prints:
// Foo
// Bar

Optimizing the use of reduce()

Functional programing is a great way to simplify a codebase. For instance, reduce is an alternative to the classic for loop, without most the boilerplate. Unfortunately, simplicity often comes at the price of performance.

Consider that you want to remove duplicate values from a Sequence. While reduce() is a perfectly fine way to express this computation, the performance will be sub optimal, because of all the unnecessary Array copying that will happen every time its closure gets called.

That's when reduce(into:_:) comes into play. This version of reduce leverages the capacities of copy-on-write type (such as Array or Dictionnary) in order to avoid unnecessary copying, which results in a great performance boost.

import Foundation

func time(averagedExecutions: Int = 1, _ code: () -> Void) {
    let start = Date()
    for _ in 0..<averagedExecutions { code() }
    let end = Date()
    
    let duration = end.timeIntervalSince(start) / Double(averagedExecutions)
    
    print("time: \(duration)")
}

let data = (1...1_000).map { _ in Int(arc4random_uniform(256)) }


// runs in 0.63s
time {
    let noDuplicates: [Int] = data.reduce([], { $0.contains($1) ? $0 : $0 + [$1] })
}

// runs in 0.15s
time {
    let noDuplicates: [Int] = data.reduce(into: [], { if !$0.contains($1) { $0.append($1) } } )
}

Avoiding hardcoded reuse identifiers

UI components such as UITableView and UICollectionView rely on reuse identifiers in order to efficiently recycle the views they display. Often, those reuse identifiers take the form of a static hardcoded String, that will be used for every instance of their class.

Through protocol-oriented programing, it's possible to avoid those hardcoded values, and instead use the name of the type as a reuse identifier.

import Foundation
import UIKit

protocol Reusable {
    static var reuseIdentifier: String { get }
}

extension Reusable {
    static var reuseIdentifier: String {
        return String(describing: self)
    }
}

extension UITableViewCell: Reusable { }

extension UITableView {
    func register<T: UITableViewCell>(_ class: T.Type) {
        register(`class`, forCellReuseIdentifier: T.reuseIdentifier)
    }
    func dequeueReusableCell<T: UITableViewCell>(for indexPath: IndexPath) -> T {
        return dequeueReusableCell(withIdentifier: T.reuseIdentifier, for: indexPath) as! T
    }
}

class MyCell: UITableViewCell { }

let tableView = UITableView()

tableView.register(MyCell.self)
let myCell: MyCell = tableView.dequeueReusableCell(for: [0, 0])

Defining a union type

The C language has a construct called union, that allows a single variable to hold values from different types. While Swift does not provide such a construct, it provides enums with associated values, which allows us to define a type called Either that implements a union of two types.

import Foundation

enum Either<A, B> {
    case left(A)
    case right(B)
    
    func either(ifLeft: ((A) -> Void)? = nil, ifRight: ((B) -> Void)? = nil) {
        switch self {
        case let .left(a):
            ifLeft?(a)
        case let .right(b):
            ifRight?(b)
        }
    }
}

extension Bool { static func random() -> Bool { return arc4random_uniform(2) == 0 } }

var intOrString: Either<Int, String> = Bool.random() ? .left(2) : .right("Foo")

intOrString.either(ifLeft: { print($0 + 1) }, ifRight: { print($0 + "Bar") })

If you're interested by this kind of data structure, I strongly recommend that you learn more about Algebraic Data Types.

Asserting that classes have associated NIBs and vice-versa

Most of the time, when we create a .xib file, we give it the same name as its associated class. From that, if we later refactor our code and rename such a class, we run the risk of forgetting to rename the associated .xib.

While the error will often be easy to catch, if the .xib is used in a remote section of its app, it might go unnoticed for sometime. Fortunately it's possible to build custom test predicates that will assert that 1) for a given class, there exists a .nib with the same name in a given Bundle, 2) for all the .nib in a given Bundle, there exists a class with the same name.

import XCTest

public func XCTAssertClassHasNib(_ class: AnyClass, bundle: Bundle, file: StaticString = #file, line: UInt = #line) {
    let associatedNibURL = bundle.url(forResource: String(describing: `class`), withExtension: "nib")
    
    XCTAssertNotNil(associatedNibURL, "Class \"\(`class`)\" has no associated nib file", file: file, line: line)
}

public func XCTAssertNibHaveClasses(_ bundle: Bundle, file: StaticString = #file, line: UInt = #line) {
    guard let bundleName = bundle.infoDictionary?["CFBundleName"] as? String,
        let basePath = bundle.resourcePath,
        let enumerator = FileManager.default.enumerator(at: URL(fileURLWithPath: basePath),
                                                    includingPropertiesForKeys: nil,
                                                    options: [.skipsHiddenFiles, .skipsSubdirectoryDescendants]) else { return }
    
    var nibFilesURLs = [URL]()
    
    for case let fileURL as URL in enumerator {
        if fileURL.pathExtension.uppercased() == "NIB" {
            nibFilesURLs.append(fileURL)
        }
    }
    
    nibFilesURLs.map { $0.lastPathComponent }
        .compactMap { $0.split(separator: ".").first }
        .map { String($0) }
        .forEach {
            let associatedClass: AnyClass? = bundle.classNamed("\(bundleName).\($0)")
            
            XCTAssertNotNil(associatedClass, "File \"\($0).nib\" has no associated class", file: file, line: line)
        }
}

XCTAssertClassHasNib(MyFirstTableViewCell.self, bundle: Bundle(for: AppDelegate.self))
XCTAssertClassHasNib(MySecondTableViewCell.self, bundle: Bundle(for: AppDelegate.self))
        
XCTAssertNibHaveClasses(Bundle(for: AppDelegate.self))

Many thanks Benjamin Lavialle for coming up with the idea behind the second test predicate.

Small footprint type-erasing with functions

Seasoned Swift developers know it: a protocol with associated type (PAT) "can only be used as a generic constraint because it has Self or associated type requirements". When we really need to use a PAT to type a variable, the goto workaround is to use a type-erased wrapper.

While this solution works perfectly, it requires a fair amount of boilerplate code. In instances where we are only interested in exposing one particular function of the PAT, a shorter approach using function types is possible.

import Foundation
import UIKit

protocol Configurable {
    associatedtype Model
    
    func configure(with model: Model)
}

typealias Configurator<Model> = (Model) -> ()

extension UILabel: Configurable {
    func configure(with model: String) {
        self.text = model
    }
}

let label = UILabel()
let configurator: Configurator<String> = label.configure

configurator("Foo")

label.text // "Foo"

Performing animations sequentially

UIKit exposes a very powerful and simple API to perform view animations. However, this API can become a little bit quirky to use when we want to perform animations sequentially, because it involves nesting closure within one another, which produces notoriously hard to maintain code.

Nonetheless, it's possible to define a rather simple class, that will expose a really nicer API for this particular use case 👌

import Foundation
import UIKit

class AnimationSequence {
    typealias Animations = () -> Void
    
    private let current: Animations
    private let duration: TimeInterval
    private var next: AnimationSequence? = nil
    
    init(animations: @escaping Animations, duration: TimeInterval) {
        self.current = animations
        self.duration = duration
    }
    
    @discardableResult func append(animations: @escaping Animations, duration: TimeInterval) -> AnimationSequence {
        var lastAnimation = self
        while let nextAnimation = lastAnimation.next {
            lastAnimation = nextAnimation
        }
        lastAnimation.next = AnimationSequence(animations: animations, duration: duration)
        return self
    }
    
    func run() {
        UIView.animate(withDuration: duration, animations: current, completion: { finished in
            if finished, let next = self.next {
                next.run()
            }
        })
    }
}

var firstView = UIView()
var secondView = UIView()

firstView.alpha = 0
secondView.alpha = 0

AnimationSequence(animations: { firstView.alpha = 1.0 }, duration: 1)
            .append(animations: { secondView.alpha = 1.0 }, duration: 0.5)
            .append(animations: { firstView.alpha = 0.0 }, duration: 2.0)
            .run()

Debouncing a function call

Debouncing is a very useful tool when dealing with UI inputs. Consider a search bar, whose content is used to query an API. It wouldn't make sense to perform a request for every character the user is typing, because as soon as a new character is entered, the result of the previous request has become irrelevant.

Instead, our code will perform much better if we "debounce" the API call, meaning that we will wait until some delay has passed, without the input being modified, before actually performing the call.

import Foundation

func debounced(delay: TimeInterval, queue: DispatchQueue = .main, action: @escaping (() -> Void)) -> () -> Void {
    var workItem: DispatchWorkItem?
    
    return {
        workItem?.cancel()
        workItem = DispatchWorkItem(block: action)
        queue.asyncAfter(deadline: .now() + delay, execute: workItem!)
    }
}

let debouncedPrint = debounced(delay: 1.0) { print("Action performed!") }

debouncedPrint()
debouncedPrint()
debouncedPrint()

// After a 1 second delay, this gets
// printed only once to the console:

// Action performed!

Providing useful operators for Optional booleans

When we need to apply the standard boolean operators to Optional booleans, we often end up with a syntax unnecessarily crowded with unwrapping operations. By taking a cue from the world of three-valued logics, we can define a couple operators that make working with Bool? values much nicer.

import Foundation

func && (lhs: Bool?, rhs: Bool?) -> Bool? {
    switch (lhs, rhs) {
    case (false, _), (_, false):
        return false
    case let (unwrapLhs?, unwrapRhs?):
        return unwrapLhs && unwrapRhs
    default:
        return nil
    }
}

func || (lhs: Bool?, rhs: Bool?) -> Bool? {
    switch (lhs, rhs) {
    case (true, _), (_, true):
        return true
    case let (unwrapLhs?, unwrapRhs?):
        return unwrapLhs || unwrapRhs
    default:
        return nil
    }
}

false && nil // false
true && nil // nil
[true, nil, false].reduce(true, &&) // false

nil || true // true
nil || false // nil
[true, nil, false].reduce(false, ||) // true

Removing duplicate values from a Sequence

Transforming a Sequence in order to remove all the duplicate values it contains is a classic use case. To implement it, one could be tempted to transform the Sequence into a Set, then back to an Array. The downside with this approach is that it will not preserve the order of the sequence, which can definitely be a dealbreaker. Using reduce() it is possible to provide a concise implementation that preserves ordering:

import Foundation

extension Sequence where Element: Equatable {
    func duplicatesRemoved() -> [Element] {
        return reduce([], { $0.contains($1) ? $0 : $0 + [$1] })
    }
}

let data = [2, 5, 2, 3, 6, 5, 2]

data.duplicatesRemoved() // [2, 5, 3, 6]

Shorter syntax to deal with optional strings

Optional strings are very common in Swift code, for instance many objects from UIKit expose the text they display as a String?. Many times you will need to manipulate this data as an unwrapped String, with a default value set to the empty string for nil cases.

While the nil-coalescing operator (e.g. ??) is a perfectly fine way to a achieve this goal, defining a computed variable like orEmpty can help a lot in cleaning the syntax.

import Foundation
import UIKit

extension Optional where Wrapped == String {
    var orEmpty: String {
        switch self {
        case .some(let value):
            return value
        case .none:
            return ""
        }
    }
}

func doesNotWorkWithOptionalString(_ param: String) {
    // do something with `param`
}

let label = UILabel()
label.text = "This is some text."

doesNotWorkWithOptionalString(label.text.orEmpty)

Encapsulating background computation and UI update

Every seasoned iOS developers knows it: objects from UIKit can only be accessed from the main thread. Any attempt to access them from a background thread is a guaranteed crash.

Still, running a costly computation on the background, and then using it to update the UI can be a common pattern.

In such cases you can rely on asyncUI to encapsulate all the boilerplate code.

import Foundation
import UIKit

func asyncUI<T>(_ computation: @autoclosure @escaping () -> T, qos: DispatchQoS.QoSClass = .userInitiated, _ completion: @escaping (T) -> Void) {
    DispatchQueue.global(qos: qos).async {
        let value = computation()
        DispatchQueue.main.async {
            completion(value)
        }
    }
}

let label = UILabel()

func costlyComputation() -> Int { return (0..<10_000).reduce(0, +) }

asyncUI(costlyComputation()) { value in
    label.text = "\(value)"
}

Retrieving all the necessary data to build a debug view

A debug view, from which any controller of an app can be instantiated and pushed on the navigation stack, has the potential to bring some real value to a development process. A requirement to build such a view is to have a list of all the classes from a given Bundle that inherit from UIViewController. With the following extension, retrieving this list becomes a piece of cake 🍰

import Foundation
import UIKit
import ObjectiveC

extension Bundle {
    func viewControllerTypes() -> [UIViewController.Type] {
        guard let bundlePath = self.executablePath else { return [] }
        
        var size: UInt32 = 0
        var rawClassNames: UnsafeMutablePointer<UnsafePointer<Int8>>!
        var parsedClassNames = [String]()
        
        rawClassNames = objc_copyClassNamesForImage(bundlePath, &size)
        
        for index in 0..<size {
            let className = rawClassNames[Int(index)]
            
            if let name = NSString.init(utf8String:className) as String?,
                NSClassFromString(name) is UIViewController.Type {
                parsedClassNames.append(name)
            }
        }
        
        return parsedClassNames
            .sorted()
            .compactMap { NSClassFromString($0) as? UIViewController.Type }
    }
}

// Fetch all view controller types in UIKit
Bundle(for: UIViewController.self).viewControllerTypes()

I share the credit for this tip with Benoît Caron.

Defining a function to map over dictionaries

Update As it turns out, map is actually a really bad name for this function, because it does not preserve composition of transformations, a property that is required to fit the definition of a real map function.

Surprisingly enough, the standard library doesn't define a map() function for dictionaries that allows to map both keys and values into a new Dictionary. Nevertheless, such a function can be helpful, for instance when converting data across different frameworks.

import Foundation

extension Dictionary {
    func map<T: Hashable, U>(_ transform: (Key, Value) throws -> (T, U)) rethrows -> [T: U] {
        var result: [T: U] = [:]
        
        for (key, value) in self {
            let (transformedKey, transformedValue) = try transform(key, value)
            result[transformedKey] = transformedValue
        }
        
        return result
    }
}

let data = [0: 5, 1: 6, 2: 7]
data.map { ("\($0)", $1 * $1) } // ["2": 49, "0": 25, "1": 36]

A shorter syntax to remove nil values

Swift provides the function compactMap(), that can be used to remove nil values from a Sequence of optionals when calling it with an argument that just returns its parameter (i.e. compactMap { $0 }). Still, for such use cases it would be nice to get rid of the trailing closure.

The implementation isn't as straightforward as your usual extension, but once it has been written, the call site definitely gets cleaner 👌

import Foundation

protocol OptionalConvertible {
    associatedtype Wrapped
    func asOptional() -> Wrapped?
}

extension Optional: OptionalConvertible {
    func asOptional() -> Wrapped? {
        return self
    }
}

extension Sequence where Element: OptionalConvertible {
    func compacted() -> [Element.Wrapped] {
        return compactMap { $0.asOptional() }
    }
}

let data = [nil, 1, 2, nil, 3, 5, nil, 8, nil]
data.compacted() // [1, 2, 3, 5, 8]

Dealing with expirable values

It might happen that your code has to deal with values that come with an expiration date. In a game, it could be a score multiplier that will only last for 30 seconds. Or it could be an authentication token for an API, with a 15 minutes lifespan. In both instances you can rely on the type Expirable to encapsulate the expiration logic.

import Foundation

struct Expirable<T> {
    private var innerValue: T
    private(set) var expirationDate: Date
    
    var value: T? {
        return hasExpired() ? nil : innerValue
    }
    
    init(value: T, expirationDate: Date) {
        self.innerValue = value
        self.expirationDate = expirationDate
    }
    
    init(value: T, duration: Double) {
        self.innerValue = value
        self.expirationDate = Date().addingTimeInterval(duration)
    }
    
    func hasExpired() -> Bool {
        return expirationDate < Date()
    }
}

let expirable = Expirable(value: 42, duration: 3)

sleep(2)
expirable.value // 42
sleep(2)
expirable.value // nil

I share the credit for this tip with Benoît Caron.

Using parallelism to speed-up map()

Almost all Apple devices able to run Swift code are powered by a multi-core CPU, consequently making a good use of parallelism is a great way to improve code performance. map() is a perfect candidate for such an optimization, because it is almost trivial to define a parallel implementation.

import Foundation

extension Array {
    func parallelMap<T>(_ transform: (Element) -> T) -> [T] {
        let res = UnsafeMutablePointer<T>.allocate(capacity: count)
        
        DispatchQueue.concurrentPerform(iterations: count) { i in
            res[i] = transform(self[i])
        }
        
        let finalResult = Array<T>(UnsafeBufferPointer(start: res, count: count))
        res.deallocate(capacity: count)
        
        return finalResult
    }
}

let array = (0..<1_000).map { $0 }

func work(_ n: Int) -> Int {
    return (0..<n).reduce(0, +)
}

array.parallelMap { work($0) }

🚨 Make sure to only use parallelMap() when the transform function actually performs some costly computations. Otherwise performances will be systematically slower than using map(), because of the multithreading overhead.

Measuring execution time with minimum boilerplate

During development of a feature that performs some heavy computations, it can be helpful to measure just how much time a chunk of code takes to run. The time() function is a nice tool for this purpose, because of how simple it is to add and then to remove when it is no longer needed.

import Foundation

func time(averagedExecutions: Int = 1, _ code: () -> Void) {
    let start = Date()
    for _ in 0..<averagedExecutions { code() }
    let end = Date()
    
    let duration = end.timeIntervalSince(start) / Double(averagedExecutions)
    
    print("time: \(duration)")
}

time {
    (0...10_000).map { $0 * $0 }
}
// time: 0.183973908424377

Running two pieces of code in parallel

Concurrency is definitely one of those topics were the right encapsulation bears the potential to make your life so much easier. For instance, with this piece of code you can easily launch two computations in parallel, and have the results returned in a tuple.

import Foundation

func parallel<T, U>(_ left: @autoclosure () -> T, _ right: @autoclosure () -> U) -> (T, U) {
    var leftRes: T?
    var rightRes: U?
    
    DispatchQueue.concurrentPerform(iterations: 2, execute: { id in
        if id == 0 {
            leftRes = left()
        } else {
            rightRes = right()
        }
    })
    
    return (leftRes!, rightRes!)
}

let values = (1...100_000).map { $0 }

let results = parallel(values.map { $0 * $0 }, values.reduce(0, +))

Making good use of #file, #line and #function

Swift exposes three special variables #file, #line and #function, that are respectively set to the name of the current file, line and function. Those variables become very useful when writing custom logging functions or test predicates.

import Foundation

func log(_ message: String, _ file: String = #file, _ line: Int = #line, _ function: String = #function) {
    print("[\(file):\(line)] \(function) - \(message)")
}

func foo() {
    log("Hello world!")
}

foo() // [MyPlayground.playground:8] foo() - Hello world!

Comparing Optionals through Conditional Conformance

Swift 4.1 has introduced a new feature called Conditional Conformance, which allows a type to implement a protocol only when its generic type also does.

With this addition it becomes easy to let Optional implement Comparable only when Wrapped also implements Comparable:

import Foundation

extension Optional: Comparable where Wrapped: Comparable {
    public static func < (lhs: Optional, rhs: Optional) -> Bool {
        switch (lhs, rhs) {
        case let (lhs?, rhs?):
            return lhs < rhs
        case (nil, _?):
            return true // anything is greater than nil
        case (_?, nil):
            return false // nil in smaller than anything
        case (nil, nil):
            return true // nil is not smaller than itself
        }
    }
}

let data: [Int?] = [8, 4, 3, nil, 12, 4, 2, nil, -5]
data.sorted() // [nil, nil, Optional(-5), Optional(2), Optional(3), Optional(4), Optional(4), Optional(8), Optional(12)]

Safely subscripting a Collection

Any attempt to access an Array beyond its bounds will result in a crash. While it's possible to write conditions such as if index < array.count { array[index] } in order to prevent such crashes, this approach will rapidly become cumbersome.

A great thing is that this condition can be encapsulated in a custom subscript that will work on any Collection:

import Foundation

extension Collection {
    subscript (safe index: Index) -> Element? {
        return indices.contains(index) ? self[index] : nil
    }
}

let data = [1, 3, 4]

data[safe: 1] // Optional(3)
data[safe: 10] // nil

Easier String slicing using ranges

Subscripting a string with a range can be very cumbersome in Swift 4. Let's face it, no one wants to write lines like someString[index(startIndex, offsetBy: 0)..<index(startIndex, offsetBy: 10)] on a regular basis.

Luckily, with the addition of one clever extension, strings can be sliced as easily as arrays 🎉

import Foundation

extension String {
    public subscript(value: CountableClosedRange<Int>) -> Substring {
        get {
            return self[index(startIndex, offsetBy: value.lowerBound)...index(startIndex, offsetBy: value.upperBound)]
        }
    }
    
    public subscript(value: CountableRange<Int>) -> Substring {
        get {
            return self[index(startIndex, offsetBy: value.lowerBound)..<index(startIndex, offsetBy: value.upperBound)]
        }
    }
    
    public subscript(value: PartialRangeUpTo<Int>) -> Substring {
        get {
            return self[..<index(startIndex, offsetBy: value.upperBound)]
        }
    }
    
    public subscript(value: PartialRangeThrough<Int>) -> Substring {
        get {
            return self[...index(startIndex, offsetBy: value.upperBound)]
        }
    }
    
    public subscript(value: PartialRangeFrom<Int>) -> Substring {
        get {
            return self[index(startIndex, offsetBy: value.lowerBound)...]
        }
    }
}

let data = "This is a string!"

data[..<4]  // "This"
data[5..<9] // "is a"
data[10...] // "string!"

Concise syntax for sorting using a KeyPath

By using a KeyPath along with a generic type, a very clean and concise syntax for sorting data can be implemented:

import Foundation

extension Sequence {
    func sorted<T: Comparable>(by attribute: KeyPath<Element, T>) -> [Element] {
        return sorted(by: { $0[keyPath: attribute] < $1[keyPath: attribute] })
    }
}

let data = ["Some", "words", "of", "different", "lengths"]

data.sorted(by: \.count) // ["of", "Some", "words", "lengths", "different"]

If you like this syntax, make sure to checkout KeyPathKit!

Manufacturing cache-efficient versions of pure functions

By capturing a local variable in a returned closure, it is possible to manufacture cache-efficient versions of pure functions. Be careful though, this trick only works with non-recursive function!

import Foundation

func cached<In: Hashable, Out>(_ f: @escaping (In) -> Out) -> (In) -> Out {
    var cache = [In: Out]()
    
    return { (input: In) -> Out in
        if let cachedValue = cache[input] {
            return cachedValue
        } else {
            let result = f(input)
            cache[input] = result
            return result
        }
    }
}

let cachedCos = cached { (x: Double) in cos(x) }

cachedCos(.pi * 2) // value of cos for 2π is now cached

Simplifying complex conditions with pattern matching

When distinguishing between complex boolean conditions, using a switch statement along with pattern matching can be more readable than the classic series of if {} else if {}.

import Foundation

let expr1: Bool
let expr2: Bool
let expr3: Bool

if expr1 && !expr3 {
    functionA()
} else if !expr2 && expr3 {
    functionB()
} else if expr1 && !expr2 && expr3 {
    functionC()
}

switch (expr1, expr2, expr3) {
    
case (true, _, false):
    functionA()
case (_, false, true):
    functionB()
case (true, false, true):
    functionC()
default:
    break
}

Easily generating arrays of data

Using map() on a range makes it easy to generate an array of data.

import Foundation

func randomInt() -> Int { return Int(arc4random()) }

let randomArray = (1...10).map { _ in randomInt() }

Using @autoclosure for cleaner call sites

Using @autoclosure enables the compiler to automatically wrap an argument within a closure, thus allowing for a very clean syntax at call sites.

import UIKit

extension UIView {
    class func animate(withDuration duration: TimeInterval, _ animations: @escaping @autoclosure () -> Void) {
        UIView.animate(withDuration: duration, animations: animations)
    }
}

let view = UIView()

UIView.animate(withDuration: 0.3, view.backgroundColor = .orange)

Observing new and old value with RxSwift

When working with RxSwift, it's very easy to observe both the current and previous value of an observable sequence by simply introducing a shift using skip().

import RxSwift

let values = Observable.of(4, 8, 15, 16, 23, 42)

let newAndOld = Observable.zip(values, values.skip(1)) { (previous: $0, current: $1) }
    .subscribe(onNext: { pair in
        print("current: \(pair.current) - previous: \(pair.previous)")
    })

//current: 8 - previous: 4
//current: 15 - previous: 8
//current: 16 - previous: 15
//current: 23 - previous: 16
//current: 42 - previous: 23

Implicit initialization from literal values

Using protocols such as ExpressibleByStringLiteral it is possible to provide an init that will be automatically when a literal value is provided, allowing for nice and short syntax. This can be very helpful when writing mock or test data.

import Foundation

extension URL: ExpressibleByStringLiteral {
    public init(stringLiteral value: String) {
        self.init(string: value)!
    }
}

let url: URL = "http://www.google.fr"

NSURLConnection.canHandle(URLRequest(url: "http://www.google.fr"))

Achieving systematic validation of data

Through some clever use of Swift private visibility it is possible to define a container that holds any untrusted value (such as a user input) from which the only way to retrieve the value is by making it successfully pass a validation test.

import Foundation

struct Untrusted<T> {
    private(set) var value: T
}

protocol Validator {
    associatedtype T
    static func validation(value: T) -> Bool
}

extension Validator {
    static func validate(untrusted: Untrusted<T>) -> T? {
        if self.validation(value: untrusted.value) {
            return untrusted.value
        } else {
            return nil
        }
    }
}

struct FrenchPhoneNumberValidator: Validator {
    static func validation(value: String) -> Bool {
       return (value.count) == 10 && CharacterSet(charactersIn: value).isSubset(of: CharacterSet.decimalDigits)
    }
}

let validInput = Untrusted(value: "0122334455")
let invalidInput = Untrusted(value: "0123")

FrenchPhoneNumberValidator.validate(untrusted: validInput) // returns "0122334455"
FrenchPhoneNumberValidator.validate(untrusted: invalidInput) // returns nil

Implementing the builder pattern with keypaths

With the addition of keypaths in Swift 4, it is now possible to easily implement the builder pattern, that allows the developer to clearly separate the code that initializes a value from the code that uses it, without the burden of defining a factory method.

import UIKit

protocol With {}

extension With where Self: AnyObject {
    @discardableResult
    func with<T>(_ property: ReferenceWritableKeyPath<Self, T>, setTo value: T) -> Self {
        self[keyPath: property] = value
        return self
    }
}

extension UIView: With {}

let view = UIView()

let label = UILabel()
    .with(\.textColor, setTo: .red)
    .with(\.text, setTo: "Foo")
    .with(\.textAlignment, setTo: .right)
    .with(\.layer.cornerRadius, setTo: 5)

view.addSubview(label)

🚨 The Swift compiler does not perform OS availability checks on properties referenced by keypaths. Any attempt to use a KeyPath for an unavailable property will result in a runtime crash.

I share the credit for this tip with Marion Curtil.

Storing functions rather than values

When a type stores values for the sole purpose of parametrizing its functions, it’s then possible to not store the values but directly the function, with no discernable difference at the call site.

import Foundation

struct MaxValidator {
    let max: Int
    let strictComparison: Bool
    
    func isValid(_ value: Int) -> Bool {
        return self.strictComparison ? value < self.max : value <= self.max
    }
}

struct MaxValidator2 {
    var isValid: (_ value: Int) -> Bool
    
    init(max: Int, strictComparison: Bool) {
        self.isValid = strictComparison ? { $0 < max } : { $0 <= max }
    }
}

MaxValidator(max: 5, strictComparison: true).isValid(5) // false
MaxValidator2(max: 5, strictComparison: false).isValid(5) // true

Defining operators on function types

Functions are first-class citizen types in Swift, so it is perfectly legal to define operators for them.

import Foundation

let firstRange = { (0...3).contains($0) }
let secondRange = { (5...6).contains($0) }

func ||(_ lhs: @escaping (Int) -> Bool, _ rhs: @escaping (Int) -> Bool) -> (Int) -> Bool {
    return { value in
        return lhs(value) || rhs(value)
    }
}

(firstRange || secondRange)(2) // true
(firstRange || secondRange)(4) // false
(firstRange || secondRange)(6) // true

Typealiases for functions

Typealiases are great to express function signatures in a more comprehensive manner, which then enables us to easily define functions that operate on them, resulting in a nice way to write and use some powerful API.

import Foundation

typealias RangeSet = (Int) -> Bool

func union(_ left: @escaping RangeSet, _ right: @escaping RangeSet) -> RangeSet {
    return { left($0) || right($0) }
}

let firstRange = { (0...3).contains($0) }
let secondRange = { (5...6).contains($0) }

let unionRange = union(firstRange, secondRange)

unionRange(2) // true
unionRange(4) // false

Encapsulating state within a function

By returning a closure that captures a local variable, it's possible to encapsulate a mutable state within a function.

import Foundation

func counterFactory() -> () -> Int {
    var counter = 0
    
    return {
        counter += 1
        return counter
    }
}

let counter = counterFactory()

counter() // returns 1
counter() // returns 2

Generating all cases for an Enum

⚠️ Since Swift 4.2, allCases can now be synthesized at compile-time by simply conforming to the protocol CaseIterable. The implementation below should no longer be used in production code.

Through some clever leveraging of how enums are stored in memory, it is possible to generate an array that contains all the possible cases of an enum. This can prove particularly useful when writing unit tests that consume random data.

import Foundation

enum MyEnum { case first; case second; case third; case fourth }

protocol EnumCollection: Hashable {
    static var allCases: [Self] { get }
}

extension EnumCollection {
    public static var allCases: [Self] {
        var i = 0
        return Array(AnyIterator {
            let next = withUnsafePointer(to: &i) {
                $0.withMemoryRebound(to: Self.self, capacity: 1) { $0.pointee }
            }
            if next.hashValue != i { return nil }
            i += 1
            return next
        })
    }
}

extension MyEnum: EnumCollection { }

MyEnum.allCases // [.first, .second, .third, .fourth]

Using map on optional values

The if-let syntax is a great way to deal with optional values in a safe manner, but at times it can prove to be just a little bit to cumbersome. In such cases, using the Optional.map() function is a nice way to achieve a shorter code while retaining safeness and readability.

import UIKit

let date: Date? = Date() // or could be nil, doesn't matter
let formatter = DateFormatter()
let label = UILabel()

if let safeDate = date {
    label.text = formatter.string(from: safeDate)
}

label.text = date.map { return formatter.string(from: $0) }

label.text = date.map(formatter.string(from:)) // even shorter, tough less readable

📣 NEW 📣 Swift Tips are now available on YouTube 👇

Summary

Tips


Download Details:

Author: vincent-pradeilles
Source code: https://github.com/vincent-pradeilles/swift-tips

License: MIT license
#swift 

Gordon  Taylor

Gordon Taylor

1653644536

Jest-html-reporters: Reporter for Jest Test Framework

Jest reporter

Jest test results processor for generating a summary in HTML

example picture

Installation


 npm install jest-html-reporters --save-dev

Usage


Configure Jest to process the test results by adding the following entry to the Jest config (jest.config.json):

"jest": {
  ...,
  "reporters": [
    "default",
    "jest-html-reporters"
  ],
  ...
}

As you run Jest from within the terminal, a file called jest_html_reporters.html will be created within your root folder containing information about your tests.

Available Options

The options below are specific to the reporter.

Option Nameenv variables nameTypeDefaultDescription
publicPathJEST_HTML_REPORTERS_PUBLIC_PATHstring''specify the base path
filenameJEST_HTML_REPORTERS_FILE_NAMEstringjest_html_reporters.htmlFilename of saved report
Applies to the generated html
expandJEST_HTML_REPORTERS_EXPANDBooleanfalsespecify whether default expand all data
pageTitleJEST_HTML_REPORTERS_PAGE_TITLEstringReportspecify header and page title
logoImgPathJEST_HTML_REPORTERS_LOGO_IMG_PATHstringundefinedspecify path of the image that will be displayed to the right of page title
hideIconJEST_HTML_REPORTERS_HIDE_ICONbooleanfalsehide default icon
customInfosJEST_HTML_REPORTERS_CUSTOM_INFOSarrayundefinedshow some custom data info in the report, example value [ {title: 'test1', value: 'test1'}, {title: 'test2', value: 'test2'}], you can also set value to a environment variable JEST_HTML_REPORTERS_CUSTOM_INFOS, see detail in #32
testCommandJEST_HTML_REPORTERS_TEST_COMMANDstring"npx jest"copy command content to quickly run test file
openReportJEST_HTML_REPORTERS_OPEN_REPORTjsonin dev=true, rest=falseoptions for npm package open
env variable support onlyJEST_HTML_REPORTERS_TEMP_DIR_PATHstringsystem default temporary directorypath to a temporary folder with attachments
failureMessageOnlyJEST_HTML_REPORTERS_FAILURE_MESSAGE_ONLYbooleanfalseshow failure test suites messages only in HTML report
enableMergeDataJEST_HTML_REPORTERS_ENABLE_MERGE_DATAbooleanfalsefor default enable merge test data feature
dataMergeLevelJEST_HTML_REPORTERS_DATA_MERGE_LEVELnumber1default merge test data level
inlineSourceJEST_HTML_REPORTERS_INLINE_SOURCEbooleanfalseOption to save report in a single combined HTML file #184

example add config options

...,
"reporters": [
  "default",
  ["jest-html-reporters", {
    "publicPath": "./html-report",
    "filename": "report.html",
    "openReport": true
  }]
]

some features.

  • Collapsable Test Groups

This feature regrading to #37, if a test file has many test cases, here will show a Merge Data checkbox on the expanded table. You can check it to merge data and set the merge level to control how to combine those data.

For Example merge data example

  • Attach screenshot to report

This feature regrading to #36, this package will a new method named addAttach.

interface IAddAttachParams {
    attach: string | Buffer;
    description: string;
    context: any;
    bufferFormat: string;
}

There are three params of this method, description is easy to understand. The param attach referring to the image, you can pass a buffer or string, if it was a buffer the package will help you create a dir named jest-html-reporters-attach and save that buffer as a jpg image in it under the publicPath. if you have already saved the image, just pass the image's path as the attach param. context is an optional parameter. Here can be specified context (default is this.global).

Here is an Example with puppeteer.

// Example attach with **buffer**
const { addAttach } = require("jest-html-reporters/helper");
const puppeteer = require("puppeteer");

describe("just examples", () => {
  test("test buffer", async () => {
    const browser = await puppeteer.launch();
    const page = await browser.newPage();
    await page.goto("https://www.google.com");
    const data = await page.screenshot();
    await browser.close();
    await addAttach({
      attach: data,
      description: 'img 1',
    });
    await addAttach({
      attach: await fs.readFileSync('./test.mp4'),
      description: 'img 1',
      bufferFormat: 'mp4',
    });
    expect(1).toBe(1);
  });
});
// Example attach with **string**
const { addAttach } = require("jest-html-reporters/helper");
const puppeteer = require("puppeteer");
const path = require("path");

describe("just examples", () => {
  test("case string", async () => {
    const filePath = path.resolve(__dirname, "./test.jpg");
    await browser.close();
    await addAttach({
      attach: filePath,
      description: 'test google 2',
    });

    await addAttach({
      attach: 'www.example.com/test.mp4',
      description: 'test video 2',
    });
    expect(1).toBe(2);
  });
});

it will show like this example

  • Attach a message to the report

This feature is in regards to #63 & #64. It allows you to add a message or log something to the html report with addMsg()

/**
 * @param {object} options - options object
 * @param {string} options.message - message string
 * @param {any} [options.context] - custom context (optional)
 */
const addMsg = async ({ message, context }) => { ... }

Only one parameter is required. If you stringify an object like this JSON.stringify(object, null, 2), the object will be prettified. context is an optional parameter. Here can be specified context (default is this.global).

Here is an Example with Nightmare.

const { addAttach, addMsg } = require("jest-html-reporters/helper");
const Nightmare = require("nightmare");

describe("Yet another example", () => {
  test("Both addAttach & addMsg with failure", async () => {
    const nightmare = Nightmare({ show: true });
    await addMsg({ message: JSON.stringify({ won: 1, too: 2 }, null, 2) });
    await nightmare.goto("https://duckduckgo.com");
    const s1 = await nightmare.screenshot();
    await addAttach(s1, "test duckduckgo 1");
    await nightmare.end();
    await addMsg({ message: JSON.stringify(process, null, 2) });
    expect(2).toEqual(1);
  }, 20000);
  test("addMsg with success", async () => {
    await addMsg({ message: JSON.stringify({ free: 3, for: 4 }, null, 2) });
    expect(2).toEqual(2);
  });
});

example

Message still displays without screenshots and with a successful test example

Author: Hazyzh
Source Code: https://github.com/Hazyzh/jest-html-reporters 
License: MIT license

#javascript #jest #testing #html 

Duong Tran

Duong Tran

1630959000

Hiển Thị Dữ Liệu Người Dùng Ra View (READ) với ReactJS

Trong video #37, chúng ta đã cùng nhau viết API lấy thông tin tất cả người dúng phía Node.js Server. Trong video này, chúng ta sẽ kết hợp API này với React để hiển thị thông tin người dùng vào một table.
👉 Đây là video 02 trong serires học nhanh CRUD với ReactJS


🧠 Nội dung video:
0:00 Giới thiệu 
0:20 Review bài học trước
1:15 Cách tìm tài liệu
4:15 Nội dung bài học
8:48 Sửa component chính
14:50 Tạo table
22:00 Gọi API
28:15 Sử dụng query param với GET
30:45 Tạo biến lưu state
39:40 Dùng Fragment
52:50 Review các files thay đổi

 #reactjs