Rails API

We are going to create a lightweight Rails application that will provide JSON representations of it's resources.

This is a simple API for a Blog. It will have User, Article and Comment resources.

Objective

• Use the Rails API Gem to generate a minimal Rails app that will be used only as an API.
• Configure each JSON Resource representation, attributes/properties, using the Active Model Serializer gem.
• Implement Cross-origin resource sharing, CORS, so that Single Page Applications, SPA can access this API.
  • SPA's created with Javascript Frameworks, (Angular, Ember, etc.), are all the rage now.

THIS REPO ONLY CONTAINS DIRECTIONS AND THE THE FINISHED LESSON THAT IS GENERATED BY THE BELOW STEPS

Each of us will be creating a new API project by following the directions below.

Demo - Code Along

• Run this project, this is the completed API we will be creating.

   rake db:create
   rake db:migrate
   rake db:seed
   rails server 
  

• Install the Chrome Extensions, JSON Prettfier, Postman Chrome Extension and Postman Launcher.

• In Chrome go to localhost to show all the Articles and their Comments.

Lab

Using curl or postman
For all the above view the rails server log and use the rails console to verify.

• Show all the articles
• Show the article with id = 3
• Create a new article.
• Delete an article

See "man curl", Curl Cheat Sheet and Curl API for curl info.

Demo

Your turn to Create a JSON API that will allow Users to Comment on Articles.

• cd into a directory that will contain this new app.

• Install the rails-api gem
  gem install rails-api

• Generate a "new_articles" Rails API app.
  rails-api new articles_api -d postgresql -T

  cd articles_api

  bundle
rake db:drop
rake db:create

• Notice that this app is missing the below directories.

  Show all the subdirectories.

  find . -type d
  

  Rails API is missing these directories.

  app/assets/javascripts
  app/assets/stylesheets
  app/helpers
  app/views
  tmp
  vendor
  

• The Gemfile is pretty bare.

  Missing the sass-rails, coffee-rails, jquery-rails, turbolinks and jbuilder gems.

• And this app is missing some Middleware.

  rake middleware | wc -l 
  

  Only 19 Middleware as opposed to 24 in a full Rails app.

• Generate a Article resource with scaffolding.
  rails g scaffold Article title body:text

  Notice that this scaffold generator creates much less than is typically generated. No views are generated!

• Open up the app/controllers/articles_controller.rb

  Notice how 'thin' this controller is. Missing lots of code typically found in a controller.

  It has most of default actions, missing new and edit. BUT this app only provides a JSON "Representation" of the resource. Previously we where always outputting a HTML "Representation" of the resource.

• Generate a User model.
  rails g model User email

• Generate a Comment resource.
  rails g scaffold Comment body:text user:belongs_to article:belongs_to

  Comments are just a join model between a specific user and article. The comment only contains a body that holds the comment content.

• Copy the seed file from this repos db/seeds.db to the articles_api/db/seeds.db.

  cp ../wdi_6_rails_lab_api/db/seeds.rb db/seeds.rb

• Add faker to the Gemfile, used to seed the DB, and bundle.

  gem faker

• Migrate and seed the DB.
  rake db:migrate
rake db:seed (make sure you set up the proper relationships before seeding!)

This will create 30 Users, 10 Articles and and each Article will have some Comments. Take a look at the seed file if your curious.

• Check out the routes.rb.
  Why don't we need the new and edit action?

  This is Article resource is truely a RESTFUL resource. Not cluttered up with actions to create forms.

• Add a root route for articles index.
  root 'articles#index'

  Now we have a set of Users, Articles and Comments.

• Start the server. And we see all the Articles!!!!

Lab

• Check this API using curl or postman For all the above view the rails server log and use the rails console to verify.

  • Show all the articles
  • Show the article with id = 3
  • Create a new article.
  • Delete an article

  See "man curl", Curl Cheat Sheet and Curl API for curl info.

• Read JSON API with rails-api and active_model_serializers.

• What is rails middleware?

• Identify at least three reasons why one would prefer using rails-api over rails.

Demo

Change the JSON representation for Articles and Comments.

• Add the active_model_serializers gem to the Gemfile and bundle. gem 'active_model_serializers'

• Generate a serializer for the Article resource.
  rails g serializer article

• Add the title and body attributes in the serializer. attributes :id, :title, :body

  This will constrain/limit the JSON returned for an Article to show only the id , title, body.

• restart server and got to the root.

  Notice that the updated_at and created_at columns are missing! We usually don't want to show these.

• Lets get rid of the root node in the JSON generated.

Add this to the Articles controller.

```
def default_serializer_options
	{root: false}
end
```

• Lets embed comments for each article in the JSON.

Add this to the Article serializer.
has_many :comments

• Generate a serializer for comment and add the body attribute.
  rails g serializer Comment

Now the comment only show it's id and body.

• Lets show the comment creator and user that commented. Add this to the Comment serializer.
  attributes :id, :body, :creator

   ```
   def creator
       "#{object.user.email}"
   end
   ```
  

Lab

Create a JSON API for a Song Playlist. A Song will have a title, artist, duration and price. An User will have a name and email. A Playlist will be a join btw Songs and Users.

Use the curl command and the Chrome debugger to show the JSON returned from the Song Playlist API.

Demo

Add the CORS gem. This will allow HTTP Request from pages NOT served from this Rails App.

In the config/application.rb file add the below. This will allow all clients the ability to access this API.

 # Add Rack::Cors as middleware                                             
    # WARNING: Allow ALL cross site scripting                                  
    config.middleware.use Rack::Cors do
      allow do
        # WARNING: Allow ALL cross site scripting from ALL domains             
        origins '*'
        # WARNING: Allow ALL HTTP method                                       
        resource '*', :headers => :any, :methods => [:get, :post,:delete, :opt\
ions]
      end
    end