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API

• Application Programming Interface
• Way in which one system interacts with another system via a well defined interface
  • An interface is any endpoint that can be used to take actions and consume data on a given application
  • An example of an interface is the web interface. It is a combination of data and presentation (HTML/CSS and JavaScript effects) that is consumed by the web browser. Beneficial for end users.
  • An API is beneficial for being used other systems (for example code) to consume.
• A web interface provides HTML, an API provides JSON (ruby hash)

• To see one of your model turned into json:

  • Install JSONViewer (for chrome), not needed but helps display the JSON better)
  • In the index action, instead of rendering a view, render:

  def index
    @objects = Object.all
    render json: @objects.to_json(:include => :another_object)
  end
  

  • Visit the route in your browser and see the results in JSON!
  • The above code displays all attributes from the object, to limit the response value:

  render json: @objects.to_json(only: [:title, :name, :created_at], 
                                include: [author: {only: [:name]}])
  

  • only can be used on the main object and the referenced object!
  • However, because we specified that we want this action to render JSON, we can't render HTML to our end users. We could create another route, but that is not DRY.

respond_to

• Within the action that you want to display both HTML and JSON, use the following code:

def index
  @objects = Object.all
  respond_to do |format|
    format.html {render :show}
    format.json {render json: @objects.to_json(only: [:title, :name, :created_at], 
                                               include: [author: {only: [:name]}])}
  end
end

Active Model Serializer

• Easier to serialize your models for API conversion
• Add to Gemfile: gem 'active_model_serializers'
• bundle install
• Generate the serializer for your model: rails g serializer model
• All serializers will be loccated in app/serializers
• attributes are added to give the serializer more info to return in the JSON response
• Now you can remove all the .toJSON... code and just use render json: @objects and that will call your serializer for that model and display the specified JSON.
• To add the relationship to a serializer, just follow the same convention, under the attributes , belongs_to @model
  • Remember you will need to create another serializer for that model in order to limit the JSON returned value!