Repository Ideas (DDD style) for Rails

generic_repo.rb

module GenericRepo
  def self.included(base)
    base.class_eval do
      extend ClassMethods
    end
  end
  module ClassMethods
    attr_accessor :model
    def create(params)
      puts "here we would create something, params=#{params}"
    end
    def create2(params)
      puts "create2 in GenericRepo, params=#{params}"
    end
  end
end

class D # this is the model
  def self.create(params)
    puts "this is D.create"
  end

  def self.build(params)
    puts "this is D.build, params=#{params}"
  end

  module GenericRepo::ClassMethods
    # only do this for stuff that should be available on
    # GenericRepo on class level (for all models)
  end

  @repo = Class.new do
    include GenericRepo
    self.model = D
    def self.create3(params)
      puts "create3, added later"
      puts "calling build..."
      model.build(params)
    end
    class << self
      alias_method :generic_create, :create
    end
    def self.create(param)
      puts "this is overriding the default repo one, right?"
      puts "and now we are calling the original:"
      self.generic_create(param)
    end
  end

  def self.repo
    @repo
  end

end

class E
  @repo = Class.new do
    include GenericRepo
    self.model = E
  end
  def self.repo
    @repo
  end
end

D.create("a parameter")
D.repo.create("another param")
D.repo.create2("bla")
D.repo.create3("bla2")

E.repo.create("blu")
begin
  E.repo.create3("should fail!")
  raise "oops, should have failed"
rescue NoMethodError => e
  # expected
end

Interesting idea! Have you used this in a real world project yet? Curious as I'm deciding on going down the DDD route myself. Thx.

No, I haven't used it in a real project yet: Currently I'm on Rails 3.1 with ActiveRecord, and it didn't feel right to use it: I don't see an advantage of the approach above to just having static methods on models for non-instance-related stuff. But bear in mind that my DDD experience is limited :)