Libr/app/controllers/api_controller.rb

class ApiController < ApplicationController

  def book_info
    book = Book.find_by_isbn params[:isbn]

    if book == nil
      render json: {book: nil, message: 'There is no mathched book.'}
      return
    end
    render json: book.to_json(include:[{:users => {except:[:api_key]}},:available_instance])
  end

  def user_info
    user = User.find_by_id params[:user_id]

    if user == nil
      render json: {user: nil, message: 'There is no mathched user.'}
      return
    end
    render json: user.to_json(except: [:api_key, :created_at],include:[:books])
  end

  def books
    @books = Book.paginate(:page => params[:page], :per_page => 10)
    render json: @books
  end
end