wraptive_record.rb

class BlogPost < ActiveRecord::Base
end

class MyBlog::Post
  attr_accessor :title, :author, :posted_at, :body

  def initialize(title:, author:, posted_at:, body:)
    self.title = title
    self.author = author
    self.posted_at = posted_at
    self.body = body
    freeze
  end
end

class MyBlog::PostsRepository < SimpleDelegator
  def initialize
    super(BlogPost)
  end

  def method_missing(*args, &block)
    result = super
    case result
    when ActiveRecord::Relation
      if result.many?
        convert_enumerator(result)
      else
        convert(result.first)
      end
    else
      convert(result)
    end
  end

  def convert_enumerator(result)
    Enumerator.new do |yielder|
      result.each do |value|
        yielder << convert(value)
      end
    end
  end

  def convert(result)
    case result
    when BlogPost
      MyBlog::Post.new(title: result.title, author: result.author,
                       posted_at: result.posted_at, body: result.body)
    else
      result
    end
  end
end

MyBlog::PostsRepository.first
#=> Returns an instance of MyBlog::Post

MyBlog::PostsRepository.all.to_a
#=> Returns an Array containing MyBlog::Post elements