gistfile1.rb

# DI

class Comment < ActiveRecord::Base
end

class Photo < ActiveRecord::Base
end

class Post
  def initialize(comment_repository, photo_repository)
    @comment_repository, @post_repository = comment_repository, post_repository
  end
  
  def assemble
    {
      :comments => @comment_repository.all,
      :photo => @photo_repository.all
    }
  end
end

# Non-DI
class Post
  def assemble
    {
      :comments => Comment.all,
      :photo => Photo.all
    }
  end
end