DCI

Version #1

http://mikepackdev.com/blog_posts/24-the-right-way-to-code-dci-in-ruby

# app/roles/customer.rb
module Customer
  def add_to_cart(book)
    self.cart << book
  end
end

# app/contexts/add_to_cart_context.rb
class AddToCartContext
  attr_reader :user, :book

  def self.call(user, book)
    AddToCartContext.new(user, book).call
  end

  def initialize(user, book)
    @user, @book = user, book
    @user.extend Customer
  end

  def call
    @user.add_to_cart(@book)
  end
end

class Book < ActiveRecord::Base
  validates :title, :presence => true
end

# app/controllers/book_controller.rb
class BookController < ApplicationController
  def add_to_cart
    AddToCartContext.call(current_user, Book.find(params[:id]))
  end
end

Version #2

• http://www.mikepackdev.com/blog_posts/37-dci-the-king-of-the-open-closed-principle

# app/models/user.rb
class User < ActiveRecord::Base
  # A dumb data object
end

# app/roles/customer.rb
module Customer
  def purchase(book)
    # Update the system to record purchase
  end
end

# app/use_cases/customer_purchases_book.rb
class CustomerPurchasesBook
  def initialize(user, book)
    @customer, @book = user, book
    @customer.extend(Customer)
  end

  def call
    @customer.purchase(@book)
  end
end