Controllers

APIs

You can use respond_to to tell your controller how to respond in different formats (html, json, xml). It passes the block a format object which you can call the different formats on along with a block containing a render call to specify how the controller responds to that format.

class UsersController < ApplicationController
    def index
        @users = User.all

        respond_to do |format|
        format.html # index.html.erb
        format.xml  { render :xml => @users }
        format.json { render :json => @users }
        end
    end
end

Passing :json as a key to render means Rails will call to_json on the data you pass.

Attributes to return

You can specify which attributes to include in your response by overriding the as_json method of the model you’re returning data from. Don’t override to_json as that does other stuff, as_json only handles selecting the attributes so is safer to override.

You can choose to completely override as_json, or work with it using super

class User < ActiveRecord::Base
    # Option 1: Purely overriding the #as_json method
    def as_json(_options={})
        { :name => self.name }  # NOT including the email field
    end

    # Option 2: Working with the default #as_json method
    def as_json(options={})
        super({ only: [:name] }.merge(options))
    end
end

The documentation for as_json will help you do more detailed stuff like including associations (use include: :association).

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