Serializer example

user_serializer

class UserSerializer < ActiveModel::Serializer
  attributes  :id,
              :email,
              :name, 
              :username, 
              :location,
              :description,
              :avatar_url,
              :trainer_id,
              :created_at,
              :updated_at
end

users_controller.rb

class Api::UsersController < Api::ApiController
  before_filter :user_admin?, only: :index
  before_filter :find_user, only: [:show, :update]

  def index
    render json: User.all, each_serializer: UserSerializer
  end

  def show
    render json: @user, serializer: UserSerializer, root: :user
  end

  def update
    if @user.update_attributes(params[:user])
      return render status: 200, json: @user, serializer: UserSerializer, root: :user
    else
      return render status: 422, json: {success: false, errors: @user.errors.full_messages.map{|error|{error: error}}}
    end
  end
end