Generate Sealed Class Hierarchy for Dart and Flutter

Dart Sealed Class Generator .Generate sealed class hierarchy for Dart and Flutter.

Features

  • Generate sealed class with abstract super type and data sub-classes.
  • Static factory methods. for example Result.success(data: 0).
  • Cast methods. for example a.asSuccess, a.isSuccess or a.asSuccessOrNull.
  • Three types of equality and hashCode generation : data (like kotlin data classes), identity and distinct.
  • Implement data equality with popular equatable library.
  • Support for generics. even types can be mixed.
  • Support for nullable and non-nullable types in null-safe projects.
  • Support for using one sealed type in another.
  • Support for null-safety.
  • Generate toString for data classes.
  • Generate 6 types of different matching methods. like when, maybeWhen and map.

Usage

Add dependencies in your pubspec.yaml file.

dependencies:
  sealed_annotations: ^latest.version

dev_dependencies:
  sealed_generators: ^latest.version

Import sealed_annotations.

import 'package:sealed_annotations/sealed_annotations.dart';

Add part pointing to a file which you want classes be generated in. with .sealed.dart extension.

part 'weather.sealed.dart';

Add @Sealed annotation, and an abstract private class as a manifest for generated code. For example:

@Sealed()
abstract class _Weather {
  void sunny();

  void rainy(int rain);

  void windy(double velocity, double? angle);
}

Then run the following command to generate code for you.

dart run build_runner build

The generated code will look like: (the following code is summarised)

abstract class Weather {
  const factory Weather.rainy({required int rain}) = WeatherRainy;

  bool get isRainy => this is WeatherRainy;

  WeatherRainy get asRainy => this as WeatherRainy;

  WeatherRainy? get asRainyOrNull {
    /* ... */
  }

  /* ... */

  R when<R extends Object?>({
    required R Function() sunny,
    required R Function(int rain) rainy,
    required R Function(double velocity, double? angle) windy,
  }) {
    /* ... */
  }

  R maybeWhen<R extends Object?>({
    R Function()? sunny,
    R Function(int rain)? rainy,
    R Function(double velocity, double? angle)? windy,
    required R Function(Weather weather) orElse,
  }) {
    /* ... */
  }

  void partialWhen({
    void Function()? sunny,
    void Function(int rain)? rainy,
    void Function(double velocity, double? angle)? windy,
    void Function(Weather weather)? orElse,
  }) {
    /* ... */
  }

  R map<R extends Object?>({
    required R Function(WeatherSunny sunny) sunny,
    required R Function(WeatherRainy rainy) rainy,
    required R Function(WeatherWindy windy) windy,
  }) {
    /* ... */
  }

  R maybeMap<R extends Object?>({
    R Function(WeatherSunny sunny)? sunny,
    R Function(WeatherRainy rainy)? rainy,
    R Function(WeatherWindy windy)? windy,
    required R Function(Weather weather) orElse,
  }) {
    /* ... */
  }

  void partialMap({
    void Function(WeatherSunny sunny)? sunny,
    void Function(WeatherRainy rainy)? rainy,
    void Function(WeatherWindy windy)? windy,
    void Function(Weather weather)? orElse,
  }) {
    /* ... */
  }
}

class WeatherSunny extends Weather {
  /* ... */
}

class WeatherRainy extends Weather with EquatableMixin {
  WeatherRainy({required this.rain});

  final int rain;

  @override
  String toString() => 'Weather.rainy(rain: $rain)';

  @override
  List<Object?> get props => [rain];
}

class WeatherWindy extends Weather {
  /* ... */
}

Notes:

  • Prefer using factories in super class instead of sub-class constructors. like Whether.rainy() instead of WhetherRainy()
  • Minimize usage of cast methods, most of the time they can be replaced with a match method.

Equality and generated class names

You can choose between three types of equality using @WithEquality(...) annotation. Default equality is data if not specified. This will become default equality for all sub-classes. You can change equality of each sub-class by using this annotation on individual methods.

Equality types:

  • data Equality is implemented with Equatable package. It behaves like kotlin data classes.
  • identity Only identical instances are equal. It's like when you don't implement any specific equality.
  • distinct All the instances are not equal with each other. Even an instance is not equal with itself.

A basic example:

@Sealed()
abstract class _Weather {
  void sunny();

  void rainy(int rain);

  void windy(double velocity, double? angle);
}

In the proceeding example all classes will have data equality. For example if you wanted identity equality for all classes but using distinct equality for windy:

@Sealed()
@WithEquality(Equality.identity)
abstract class _Weather {
  void sunny();

  void rainy(int rain);

  @WithEquality(Equality.distinct)
  void windy(double velocity, double? angle);
}

An abstract super class is generated with name equal to name of manifest class without the underline (here Weather). Each method will become a sub-class. There should be at least one method. sub-class names are based on method name prefixed with super class name (for example WeatherSunny). Naming process can be tailored with use of @WithPrefix and @WithName annotations. Each method argument will become a field in corresponding sub-class. Field names are equal to argument names and field types are equal to argument types or dynamic if not specified. Argument types can be overridden using @WithType annotation for example when type information is not available at build time. Note that you can have nullable and non-nullable fields.

To change prefix of sub-class names which by default is top class name, you can use @WithPrefix annotation. for example:

@Sealed()
@WithPrefix('Hello')
abstract class _Weather {
  void sunny();
}

Now sunny will be named HelloSunny instead of the default WeatherSunny. You can use @WithPrefix('') to remove all prefix from sub-class names.

To change sub-class names directly you can use @WithName annotation. It will override WithPrefix if specified. for example:

@Sealed()
abstract class _Weather {
  @WithName('Hello')
  void sunny();
}

Now sunny will be named Hello instead of the default WeatherSunny. This is useful if you want not to use prefix for some items.

Almost all methods on sealed classes use short names extracted from manifest method names. Full sub-class names are not used. It is recommended not to use sub-classes directly. There are factory methods for each item on super class.

Generic Usage

For generic sealed classes you should write manifest class like a generic class which you are implementing.

It is recommended that if you want nullable generic fields, declare a generic parameter as T extends Base? and use T without nullability suffix. If you want non-nullable generic fields declare a generic parameter as T extends Base and use T without nullability suffix. If you don't specify upper bound it will default to Object? so your generic types will be nullable.

import 'package:sealed_annotations/sealed_annotations.dart';

part 'result.sealed.dart';

@Sealed()
abstract class _Result<D extends num> {
  void success(D data);

  void error(Object exception);
}

Or you can have multiple generic types and even mix them.

import 'package:sealed_annotations/sealed_annotations.dart';

part 'result.sealed.dart';

@Sealed()
abstract class _Result<D extends num, E extends Object> {
  void success(D data);

  void error(E exception);

  void mixed(D data, E exception);
}

Dynamic types and Using one sealed type in another

Consider you have a sealed result type like:

@Sealed()
abstract class _Result<D extends Object> {
  /* ... */
}

You want to use this type in another sealed type.

@Sealed()
abstract class _WeatherInfo {
  void fromInternet(Result<WeatherData> result);
}

If you generate for WeatherInfo you will see that result has dynamic type. It is because Result itself is not code generated at build time.

You should use @WithType annotation.

@Sealed()
abstract class _WeatherInfo {
  void fromInternet(@WithType('Result<WeatherData>') result);

  // you can also have nullable types.
  void nullable(@WithType('Result<WeatherData>?') result);
}

Use this package as a library

Depend on it

Run this command:

With Dart:

 $ dart pub add sealed_writer

With Flutter:

 $ flutter pub add sealed_writer

This will add a line like this to your package's pubspec.yaml (and run an implicit dart pub get):


dependencies:
  sealed_writer: ^1.7.0

Alternatively, your editor might support dart pub get or flutter pub get. Check the docs for your editor to learn more.

Import it

Now in your Dart code, you can use:

import 'package:sealed_writer/sealed_writer.dart';

example/example.dart

import 'package:sealed_writer/sealed_writer.dart';

void main() {
  final source = Manifest(
    name: 'Weather',
    items: [
      ManifestItem(
        name: 'WeatherSunny',
        shortName: 'sunny',
        equality: ManifestEquality.data,
        fields: [],
      ),
      ManifestItem(
        name: 'WeatherRainy',
        shortName: 'rainy',
        equality: ManifestEquality.data,
        fields: [
          ManifestField(
            name: 'rain',
            type: ManifestType(
              name: 'int',
              isNullable: false,
            ),
          ),
        ],
      ),
    ],
    params: [],
  );

  print('==============');
  print('FORWARD WRITER');
  print('==============');

  final forward = SourceWriter(source);
  print(forward.write());

  print('===============');
  print('BACKWARD WRITER');
  print('===============');

  final backward = BackwardWriter(source);
  print(backward.write());
}

What is GEEK

Buddha Community

Generate Sealed Class Hierarchy for Dart and Flutter

Google's Flutter 1.20 stable announced with new features - Navoki

Flutter Google cross-platform UI framework has released a new version 1.20 stable.

Flutter is Google’s UI framework to make apps for Android, iOS, Web, Windows, Mac, Linux, and Fuchsia OS. Since the last 2 years, the flutter Framework has already achieved popularity among mobile developers to develop Android and iOS apps. In the last few releases, Flutter also added the support of making web applications and desktop applications.

Last month they introduced the support of the Linux desktop app that can be distributed through Canonical Snap Store(Snapcraft), this enables the developers to publish there Linux desktop app for their users and publish on Snap Store.  If you want to learn how to Publish Flutter Desktop app in Snap Store that here is the tutorial.

Flutter 1.20 Framework is built on Google’s made Dart programming language that is a cross-platform language providing native performance, new UI widgets, and other more features for the developer usage.

Here are the few key points of this release:

Performance improvements for Flutter and Dart

In this release, they have got multiple performance improvements in the Dart language itself. A new improvement is to reduce the app size in the release versions of the app. Another performance improvement is to reduce junk in the display of app animation by using the warm-up phase.

sksl_warm-up

If your app is junk information during the first run then the Skia Shading Language shader provides for pre-compilation as part of your app’s build. This can speed it up by more than 2x.

Added a better support of mouse cursors for web and desktop flutter app,. Now many widgets will show cursor on top of them or you can specify the type of supported cursor you want.

Autofill for mobile text fields

Autofill was already supported in native applications now its been added to the Flutter SDK. Now prefilled information stored by your OS can be used for autofill in the application. This feature will be available soon on the flutter web.

flutter_autofill

A new widget for interaction

InteractiveViewer is a new widget design for common interactions in your app like pan, zoom drag and drop for resizing the widget. Informations on this you can check more on this API documentation where you can try this widget on the DartPad. In this release, drag-drop has more features added like you can know precisely where the drop happened and get the position.

Updated Material Slider, RangeSlider, TimePicker, and DatePicker

In this new release, there are many pre-existing widgets that were updated to match the latest material guidelines, these updates include better interaction with Slider and RangeSliderDatePicker with support for date range and time picker with the new style.

flutter_DatePicker

New pubspec.yaml format

Other than these widget updates there is some update within the project also like in pubspec.yaml file format. If you are a flutter plugin publisher then your old pubspec.yaml  is no longer supported to publish a plugin as the older format does not specify for which platform plugin you are making. All existing plugin will continue to work with flutter apps but you should make a plugin update as soon as possible.

Preview of embedded Dart DevTools in Visual Studio Code

Visual Studio code flutter extension got an update in this release. You get a preview of new features where you can analyze that Dev tools in your coding workspace. Enable this feature in your vs code by _dart.previewEmbeddedDevTools_setting. Dart DevTools menu you can choose your favorite page embed on your code workspace.

Network tracking

The updated the Dev tools comes with the network page that enables network profiling. You can track the timings and other information like status and content type of your** network calls** within your app. You can also monitor gRPC traffic.

Generate type-safe platform channels for platform interop

Pigeon is a command-line tool that will generate types of safe platform channels without adding additional dependencies. With this instead of manually matching method strings on platform channel and serializing arguments, you can invoke native class and pass nonprimitive data objects by directly calling the Dartmethod.

There is still a long list of updates in the new version of Flutter 1.2 that we cannot cover in this blog. You can get more details you can visit the official site to know more. Also, you can subscribe to the Navoki newsletter to get updates on these features and upcoming new updates and lessons. In upcoming new versions, we might see more new features and improvements.

You can get more free Flutter tutorials you can follow these courses:

#dart #developers #flutter #app developed #dart devtools in visual studio code #firebase local emulator suite in flutter #flutter autofill #flutter date picker #flutter desktop linux app build and publish on snapcraft store #flutter pigeon #flutter range slider #flutter slider #flutter time picker #flutter tutorial #flutter widget #google flutter #linux #navoki #pubspec format #setup flutter desktop on windows

Terry  Tremblay

Terry Tremblay

1598396940

What is Flutter and why you should learn it?

Flutter is an open-source UI toolkit for mobile developers, so they can use it to build native-looking** Android and iOS** applications from the same code base for both platforms. Flutter is also working to make Flutter apps for Web, PWA (progressive Web-App) and Desktop platform (Windows,macOS,Linux).

flutter-mobile-desktop-web-embedded_min

Flutter was officially released in December 2018. Since then, it has gone a much stronger flutter community.

There has been much increase in flutter developers, flutter packages, youtube tutorials, blogs, flutter examples apps, official and private events, and more. Flutter is now on top software repos based and trending on GitHub.

Flutter meaning?

What is Flutter? this question comes to many new developer’s mind.

humming_bird_dart_flutter

Flutter means flying wings quickly, and lightly but obviously, this doesn’t apply in our SDK.

So Flutter was one of the companies that were acquired by **Google **for around $40 million. That company was based on providing gesture detection and recognition from a standard webcam. But later when the Flutter was going to release in alpha version for developer it’s name was Sky, but since Google already owned Flutter name, so they rename it to Flutter.

Where Flutter is used?

Flutter is used in many startup companies nowadays, and even some MNCs are also adopting Flutter as a mobile development framework. Many top famous companies are using their apps in Flutter. Some of them here are

Dream11

Dream11

NuBank

NuBank

Reflectly app

Reflectly app

Abbey Road Studios

Abbey Road Studios

and many more other apps. Mobile development companies also adopted Flutter as a service for their clients. Even I was one of them who developed flutter apps as a freelancer and later as an IT company for mobile apps.

Flutter as a service

#dart #flutter #uncategorized #flutter framework #flutter jobs #flutter language #flutter meaning #flutter meaning in hindi #google flutter #how does flutter work #what is flutter

Adobe XD plugin for Flutter with CodePen Tutorial

Recently Adobe XD releases a new version of the plugin that you can use to export designs directly into flutter widgets or screens. Yes, you read it right, now you can make and export your favorite design in Adobe XD and export all the design in the widget form or as a full-screen design, this can save you a lot of time required in designing.

What we will do?
I will make a simple design of a dialogue box with a card design with text over it as shown below. After you complete this exercise you can experiment with the UI. You can make your own components or import UI kits available with the Adobe XD.

#developers #flutter #adobe xd design export to flutter #adobe xd flutter code #adobe xd flutter code generator - plugin #adobe xd flutter plugin #adobe xd flutter plugin tutorial #adobe xd plugins #adobe xd to flutter #adobe xd tutorial #codepen for flutter.

6 Things About HTTP Request in Dart For Beginners

Introduction

If you are here and a beginner, that means you want to learn everything about making an API request using Dart in Flutter, then you are in the right place for the HTTP tutorial. So without wasting any time, let’s start with this flutter tutorial. We will cover the essential topics required to work with the HTTP request in Dart.

What is Rest API in Dart ?

rest api flow

Rest APIs are a way to fetch data from the internet in flutter or communicate the server from the app and get some essential information from your server to the app. This information can be regarding your app’s data, user’s data, or any data you want to share globally from your app to all of your users.

This HTTP request fetches in a unique JSON format, and then the information is fetched from the JSON and put in the UI of the app.

Every programming language has a way of some internet connectivity i.e, use this rest API developed on the server and fetch data from the internet. To use this request feature, we have to add HTTP package in flutter, add this flutter package add in your project to use the http feature. Add this HTTP package to your pubspec.yaml, and run a command in terminal :

flutter packages get

#dart #flutter #async await #async function #cancel http api request in flutter #fetch data from the internet #flutter cancel future #flutter get request example #flutter post request example #future of flutter #http tutorial

Martin  Soit

Martin Soit

1597029709

Dart Generators and Callable Class in Flutter

In this blog, we will explore Dart Generators & Callable Class In Flutter. We will perceive how to utilize Dart’s generator capacity to create an on-request sequence of qualities synchronously and asynchronously is the iterative and recursive way and Furthermore,

We will figure out how to implement a Callable class. Dart is a genuine object-oriented language. Dart’s functions are additionally objects.

Table of Content :

Dart Generators — Introduction
Synchronous Generator
Asynchronous Generator
Recursive Synchronous Generator
Recursive Asynchronous Generator
Callable Class — Introduction
Implement Callable Class
Using Callable Class
Conclusion

Dart Generators

It is Functions are utilized to create an arrangement of values on-demand lazily. Such a value arrangement can be produced either synchronously or asynchronously.

There are two sorts of implicit generator functions accessible to support the two situations :

Synchronous Generator
Asynchronous Generator

#generator #callable #flutter #dart #mobile-app-development