21 API NotesController

API-specific controller

Let's add a new controller just for the api, and since we want this to have a similar RESTful structure as the rest of our app, let's namespace it under /api. That way /api/notes.json is a different action than the one we hit with the existing notes#index route.

Additionally, let's namespace it under a version number, so if we have to change this API in the future, the old API will keep working. We don't want to break backwards compatibility with clients that integrated against older versions of the API.

Create a new route in config/routes.rb:

namespace :api do
  namespace :v1 do
    resources :notes
  end
end

Rails is going to expect our namespaced controller to be Api::V1::NotesController, because that's how the Rails Inflector works unless we tell it otherwise.

http://api.rubyonrails.org/classes/ActiveSupport/Inflector.html

The Inflector transforms words from singular to plural, class names to table names, modularized class names to ones without, and class names to foreign keys.

We'd prefer API to Api, so we'll add a custom inflector:

config/initialisers/inflections.rb

inflect.acronym 'API'

Having done that, we must add the necessary folders and files to create our API-specific NotesController with an index action that responds to .json:

app/controllers/api/v1/notes_controller.rb

class API::V1::NotesController < ApplicationController
  def index
    @notes = Note.all
    respond_to do |format|
      format.json do
        render json: @notes.to_json
      end
    end
  end
end

The to_json method can be called on any ActiveRecord model or relation, and we just called it on a relation, to return a collection of JSON hashes inside an array. However, using to_json in this way is not a good design for an API that we don't want to change.

Next: API Jbuilder Views