DCI + Rails new and create

dci-rest-creation.rb

# ---role

module BookSeller
  def create_book(params)
    self.books.create! params
  end
end

# ---context

class AddingBookContext
  attr_accessor :user, :book
  
  def initialize(user_id)
    @user = User.find(user_id)
    @book = Book.new(:user => @user)
    @user.extend BookSeller
  end

  def execute(params)
    @user.create_book(params)
  end
end

# ---controller


class BookController < ApplicationController
  before_filter :create_context, :only => [:new,:create]
  def new
    @book = @adding_book_context.book
  end

  def create
    @adding_book_context.execute(params)
  end
  
  private
    def create_context
      @adding_book_context = AddingBookContext.new(current_user.id)
    end
end