DCI example

dci_example.rb

require 'delegate'

class GuestRole < SimpleDelegator
  def books
    Book.published
  end
end

class AdminRole < SimpleDelegator
  def books
    Book.scoped
  end
end

class BooksController
  def index
    role = role_for(current_user)
    books = role.books

    render :index, locals: { books: books }
  end

  def role_for(user)
    role_name = user.role
    klass = Object.const_get("#{role_name.classify}Role")

    klass.new(user)
  end

  private :role_for
end