Mongoid and Active record linked associations

active-record-mongo-linked-associations.rb

#Extended this gist https://gist.github.com/knapo/8897592
class ActiveRecord::Base
  def self.has_many_documents(association_name)
    class_eval %<
      def #{association_name}
        #{association_name.to_s.singularize.classify}.where(#{name.underscore}_id: id)
      end
    >
  end

  def self.has_one_document(association_name,options={})
    association_class = unless options.empty?
                          options[:class_name]
                        else
                          association_name.to_s.singularize.classify
                        end
    if options.present? && options[:conditions].present?
      class_eval %<
        def #{association_name}
          #{association_class}.#{options[:conditions]}.where(#{name.underscore}_id: id).first
        end
        def #{association_name}=(object)
            @#{association_name} = object
            self.#{association_name}_id = object.try :id
        end
      >
    else
      class_eval %<
        def #{association_name}
          #{association_class}.where(#{name.underscore}_id: id).first
        end
        def #{association_name}=(object)
          @#{association_name} = object
          self.#{association_name}_id = object.try :id
        end
      >
    end

  end
end

module Mongoid::ActiveRecordBridge
  extend ActiveSupport::Concern

  included do
    def self.belongs_to_record(association_name, options={})
      association_class = options[:class_name] || association_name.to_s.singularize.classify
      class_eval %<
        field :#{association_name}_id, type: Integer
        index(#{association_name}_id: 1)

        def #{association_name}
          @#{association_name} ||= #{association_class}.where(id: #{association_name}_id).first if #{association_name}_id
        end

        def #{association_name}=(object)
          @#{association_name} = object
          self.#{association_name}_id = object.try :id
        end
      >
    end

    def self.has_one_record(association_name, options={})
      association_class = options[:class_name] || association_name.to_s.singularize.classify
      class_eval %<
        field :#{association_name}_id, type: Integer
        index(#{association_name}_id: 1)

        def #{association_name}
          @#{association_name} ||= #{association_class}.where(id: #{association_name}_id).first if #{association_name}_id
        end

        def #{association_name}=(object)
          @#{association_name} = object
          self.#{association_name}_id = object.try :id
        end
      >
    end

  end
end

class Profile < ActiveRecord::Base
  has_many_documents :users  
  has_one_document :admin, {:conditions => "where(admin: true)" , :class_name => "User" }
end

class User 
  belongs_to_record :profile
end