Ken4scholars

Ken4scholars

1570181115

Kenneth Nwafor | Django Post-save Signal in a Transaction

What are the side effects of writing code wthat can fire signals in a transaction block? Find out in this article

#python #django #web-service #database

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Sasha  Roberts

Sasha Roberts

1659500100

Reform: Form Objects Decoupled From Models In Ruby

Reform

Form objects decoupled from your models.

Reform gives you a form object with validations and nested setup of models. It is completely framework-agnostic and doesn't care about your database.

Although reform can be used in any Ruby framework, it comes with Rails support, works with simple_form and other form gems, allows nesting forms to implement has_one and has_many relationships, can compose a form from multiple objects and gives you coercion.

Full Documentation

Reform is part of the Trailblazer framework. Full documentation is available on the project site.

Reform 2.2

Temporary note: Reform 2.2 does not automatically load Rails files anymore (e.g. ActiveModel::Validations). You need the reform-rails gem, see Installation.

Defining Forms

Forms are defined in separate classes. Often, these classes partially map to a model.

class AlbumForm < Reform::Form
  property :title
  validates :title, presence: true
end

Fields are declared using ::property. Validations work exactly as you know it from Rails or other frameworks. Note that validations no longer go into the model.

The API

Forms have a ridiculously simple API with only a handful of public methods.

  1. #initialize always requires a model that the form represents.
  2. #validate(params) updates the form's fields with the input data (only the form, not the model) and then runs all validations. The return value is the boolean result of the validations.
  3. #errors returns validation messages in a classic ActiveModel style.
  4. #sync writes form data back to the model. This will only use setter methods on the model(s).
  5. #save (optional) will call #save on the model and nested models. Note that this implies a #sync call.
  6. #prepopulate! (optional) will run pre-population hooks to "fill out" your form before rendering.

In addition to the main API, forms expose accessors to the defined properties. This is used for rendering or manual operations.

Setup

In your controller or operation you create a form instance and pass in the models you want to work on.

class AlbumsController
  def new
    @form = AlbumForm.new(Album.new)
  end

This will also work as an editing form with an existing album.

def edit
  @form = AlbumForm.new(Album.find(1))
end

Reform will read property values from the model in setup. In our example, the AlbumForm will call album.title to populate the title field.

Rendering Forms

Your @form is now ready to be rendered, either do it yourself or use something like Rails' #form_for, simple_form or formtastic.

= form_for @form do |f|
  = f.input :title

Nested forms and collections can be easily rendered with fields_for, etc. Note that you no longer pass the model to the form builder, but the Reform instance.

Optionally, you might want to use the #prepopulate! method to pre-populate fields and prepare the form for rendering.

Validation

After form submission, you need to validate the input.

class SongsController
  def create
    @form = SongForm.new(Song.new)

    #=> params: {song: {title: "Rio", length: "366"}}

    if @form.validate(params[:song])

The #validate method first updates the values of the form - the underlying model is still treated as immutuable and remains unchanged. It then runs all validations you provided in the form.

It's the only entry point for updating the form. This is per design, as separating writing and validation doesn't make sense for a form.

This allows rendering the form after validate with the data that has been submitted. However, don't get confused, the model's values are still the old, original values and are only changed after a #save or #sync operation.

Syncing Back

After validation, you have two choices: either call #save and let Reform sort out the rest. Or call #sync, which will write all the properties back to the model. In a nested form, this works recursively, of course.

It's then up to you what to do with the updated models - they're still unsaved.

Saving Forms

The easiest way to save the data is to call #save on the form.

if @form.validate(params[:song])
  @form.save  #=> populates album with incoming data
              #   by calling @form.album.title=.
else
  # handle validation errors.
end

This will sync the data to the model and then call album.save.

Sometimes, you need to do saving manually.

Default values

Reform allows default values to be provided for properties.

class AlbumForm < Reform::Form
  property :price_in_cents, default: 9_95
end

Saving Forms Manually

Calling #save with a block will provide a nested hash of the form's properties and values. This does not call #save on the models and allows you to implement the saving yourself.

The block parameter is a nested hash of the form input.

  @form.save do |hash|
    hash      #=> {title: "Greatest Hits"}
    Album.create(hash)
  end

You can always access the form's model. This is helpful when you were using populators to set up objects when validating.

  @form.save do |hash|
    album = @form.model

    album.update_attributes(hash[:album])
  end

Nesting

Reform provides support for nested objects. Let's say the Album model keeps some associations.

class Album < ActiveRecord::Base
  has_one  :artist
  has_many :songs
end

The implementation details do not really matter here, as long as your album exposes readers and writes like Album#artist and Album#songs, this allows you to define nested forms.

class AlbumForm < Reform::Form
  property :title
  validates :title, presence: true

  property :artist do
    property :full_name
    validates :full_name, presence: true
  end

  collection :songs do
    property :name
  end
end

You can also reuse an existing form from elsewhere using :form.

property :artist, form: ArtistForm

Nested Setup

Reform will wrap defined nested objects in their own forms. This happens automatically when instantiating the form.

album.songs #=> [<Song name:"Run To The Hills">]

form = AlbumForm.new(album)
form.songs[0] #=> <SongForm model: <Song name:"Run To The Hills">>
form.songs[0].name #=> "Run To The Hills"

Nested Rendering

When rendering a nested form you can use the form's readers to access the nested forms.

= text_field :title,         @form.title
= text_field "artist[name]", @form.artist.name

Or use something like #fields_for in a Rails environment.

= form_for @form do |f|
  = f.text_field :title

  = f.fields_for :artist do |a|
    = a.text_field :name

Nested Processing

validate will assign values to the nested forms. sync and save work analogue to the non-nested form, just in a recursive way.

The block form of #save would give you the following data.

@form.save do |nested|
  nested #=> {title:  "Greatest Hits",
         #    artist: {name: "Duran Duran"},
         #    songs: [{title: "Hungry Like The Wolf"},
         #            {title: "Last Chance On The Stairways"}]
         #   }
  end

The manual saving with block is not encouraged. You should rather check the Disposable docs to find out how to implement your manual tweak with the official API.

Populating Forms

Very often, you need to give Reform some information how to create or find nested objects when validateing. This directive is called populator and documented here.

Installation

Add this line to your Gemfile:

gem "reform"

Reform works fine with Rails 3.1-5.0. However, inheritance of validations with ActiveModel::Validations is broken in Rails 3.2 and 4.0.

Since Reform 2.2, you have to add the reform-rails gem to your Gemfile to automatically load ActiveModel/Rails files.

gem "reform-rails"

Since Reform 2.0 you need to specify which validation backend you want to use (unless you're in a Rails environment where ActiveModel will be used).

To use ActiveModel (not recommended because very out-dated).

require "reform/form/active_model/validations"
Reform::Form.class_eval do
  include Reform::Form::ActiveModel::Validations
end

To use dry-validation (recommended).

require "reform/form/dry"
Reform::Form.class_eval do
  feature Reform::Form::Dry
end

Put this in an initializer or on top of your script.

Compositions

Reform allows to map multiple models to one form. The complete documentation is here, however, this is how it works.

class AlbumForm < Reform::Form
  include Composition

  property :id,    on: :album
  property :title, on: :album
  property :songs, on: :cd
  property :cd_id, on: :cd, from: :id
end

When initializing a composition, you have to pass a hash that contains the composees.

AlbumForm.new(album: album, cd: CD.find(1))

More

Reform comes many more optional features, like hash fields, coercion, virtual fields, and so on. Check the full documentation here.

Reform is part of the Trailblazer project. Please buy my book to support the development and learn everything about Reform - there's two chapters dedicated to Reform!

Security And Strong_parameters

By explicitly defining the form layout using ::property there is no more need for protecting from unwanted input. strong_parameter or attr_accessible become obsolete. Reform will simply ignore undefined incoming parameters.

This is not Reform 1.x!

Temporary note: This is the README and API for Reform 2. On the public API, only a few tiny things have changed. Here are the Reform 1.2 docs.

Anyway, please upgrade and report problems and do not simply assume that we will magically find out what needs to get fixed. When in trouble, join us on Gitter.

Full documentation for Reform is available online, or support us and grab the Trailblazer book. There is an Upgrading Guide to help you migrate through versions.

Attributions!!!

Great thanks to Blake Education for giving us the freedom and time to develop this project in 2013 while working on their project.


Author: trailblazer
Source code: https://github.com/trailblazer/reform
License:  MIT license

#ruby  #ruby-on-rails

Ahebwe  Oscar

Ahebwe Oscar

1620177818

Django admin full Customization step by step

Welcome to my blog , hey everyone in this article you learn how to customize the Django app and view in the article you will know how to register  and unregister  models from the admin view how to add filtering how to add a custom input field, and a button that triggers an action on all objects and even how to change the look of your app and page using the Django suit package let’s get started.

Database

Custom Titles of Django Admin

Exclude in Django Admin

Fields in Django Admin

#django #create super user django #customize django admin dashboard #django admin #django admin custom field display #django admin customization #django admin full customization #django admin interface #django admin register all models #django customization

Ahebwe  Oscar

Ahebwe Oscar

1620185280

How model queries work in Django

How model queries work in Django

Welcome to my blog, hey everyone in this article we are going to be working with queries in Django so for any web app that you build your going to want to write a query so you can retrieve information from your database so in this article I’ll be showing you all the different ways that you can write queries and it should cover about 90% of the cases that you’ll have when you’re writing your code the other 10% depend on your specific use case you may have to get more complicated but for the most part what I cover in this article should be able to help you so let’s start with the model that I have I’ve already created it.

**Read More : **How to make Chatbot in Python.

Read More : Django Admin Full Customization step by step

let’s just get into this diagram that I made so in here:

django queries aboutDescribe each parameter in Django querset

we’re making a simple query for the myModel table so we want to pull out all the information in the database so we have this variable which is gonna hold a return value and we have our myModel models so this is simply the myModel model name so whatever you named your model just make sure you specify that and we’re gonna access the objects attribute once we get that object’s attribute we can simply use the all method and this will return all the information in the database so we’re gonna start with all and then we will go into getting single items filtering that data and go to our command prompt.

Here and we’ll actually start making our queries from here to do this let’s just go ahead and run** Python manage.py shell** and I am in my project file so make sure you’re in there when you start and what this does is it gives us an interactive shell to actually start working with our data so this is a lot like the Python shell but because we did manage.py it allows us to do things a Django way and actually query our database now open up the command prompt and let’s go ahead and start making our first queries.

#django #django model queries #django orm #django queries #django query #model django query #model query #query with django

Ken4scholars

Ken4scholars

1570181115

Kenneth Nwafor | Django Post-save Signal in a Transaction

What are the side effects of writing code wthat can fire signals in a transaction block? Find out in this article

#python #django #web-service #database

Ananya Gupta

Ananya Gupta

1597123834

Main Pros and Cons of Django As A Web Framework for Python Developers

Django depicts itself as “the web system for fussbudgets with cutoff times”. It was intended to help Python engineers take applications from idea to consummation as fast as could be expected under the circumstances.

It permits fast turn of events on the off chance that you need to make a CRUD application with batteries included. With Django, you won’t need to rehash an already solved problem. It just works and lets you center around your business rationale and making something clients can utilize.

Pros of Django

“Batteries included” theory

The standard behind batteries-included methods normal usefulness for building web applications accompanies the system, not as isolated libraries.

Django incorporates much usefulness you can use to deal with normal web advancement undertakings. Here are some significant level functionalities that Django gives you, which else you need to stay together if you somehow happened to utilize a small scale structure:

ORM

Database relocations

Client validation

Administrator board

Structures

Normalized structure

Django as a system proposes the right structure of an undertaking. That structure helps designers in making sense of how and where to execute any new component.

With a generally acknowledged venture structure that is like numerous tasks, it is a lot simpler to discover online good arrangements or approach the network for help. There are numerous energetic Python designers who will assist you with comprehending any issue you may experience.

Django applications

Django applications (or applications for short) permit designers to separate a task into numerous applications. An application is whatever is introduced by putting in settings.INSTALLED_APPS. This makes it simpler for engineers to add usefulness to the web application by coordinating outer Django applications into the venture.

There are many reusable modules and applications to accelerate your turn of events learn through Online Django Class and Check the Django website.

Secure of course

Django gives great security assurance out of the crate and incorporates avoidance components for basic assaults like SQL Injection (XSS) and Cross-site Request Forgery (CSRF). You can discover more subtleties in the official security diagram control.

REST structure for building APIs

Django REST Framework, commonly condensed “DRF”, is a Python library for building APIs. It has secluded and adaptable engineering that functions admirably for both straightforward and complex web APIs.

DRF gives a lot of verification and authorization strategies out of the case. It is an adaptable, full-included library with measured and adjustable engineering. It accompanies nonexclusive classes for CRUD tasks and an implicit API program for testing API endpoints.

GraphQL structure for building APIs

Huge REST APIs regularly require a lot of solicitations to various endpoints to recover every single required datum. GraphQL it’s a question language that permits us to share related information in a lot simpler design. For a prologue to GraphQL and an outline of its ideas, if it’s not too much trouble allude to the authority GraphQL documentation.

Graphene-Django gives reflections that make it simple to add GraphQL usefulness to your Django venture. Ordinary Django models, structures, validation, consent arrangements, and different functionalities can be reused to manufacture GraphQL blueprint. It additionally gives an implicit API program for testing API endpoints.

Cons of Django

Django ORM

Django ORM, made before SQLAlchemy existed, is currently much sub-par compared to SQLAlchemy. It depends on the Active Record design which is more regrettable than the Unit of Work design embraced by SQLAlchemy. This implies, in Django, models can “spare” themselves and exchanges are off as a matter of course, they are a bit of hindsight. Peruse more in Why I kind of aversion Django.

Django advances course popularity increses day by day:

Django is huge and is viewed as strong bit of programming. This permits the network to create several reusable modules and applications yet has additionally restricted the speed of advancement of the Django. On head of that Django needs to keep up in reverse similarity, so it advances gradually.

Rundown - Should I use Django as a Python designer?

While Django ORM isn’t as adaptable as SQLAlchemy and the enormous environment of reusable modules and applications hinders structure advancement - plainly Django ought to be the best option web system for Python engineers.

Elective, light systems, similar to Flask, while offering a retreat from Django huge biological system and designs, in the long haul can require substantially more additional libraries and usefulness, in the end making many experienced Python engineers winding up wishing they’d began with Django.

Django undertaking’s security and network have become enormously over the previous decade since the system’s creation. Official documentation and instructional exercises are probably the best anyplace in programming advancement. With each delivery, Django keeps on including huge new usefulness.

#django online training #django online course #online django course #django course #django training #django certification course