Using record delegations with Mongoid Rails and Ruby

delegation, mongoid, ruby, ruby-on-rails

Solution

`delegate` method is not limited to Active record - it comes with Active Support and may be used on any class to delegate any method to any internal objects:

require 'active_support/all'
class A
  def initialize(a)
    @a = a
  end
  delegate :+, to: :@a
end

A.new(2) + 4     #=> 6

Hence you can use it as well for your models. Just remember to add `allow_nil: true` so it doesn't throw an exception if it has no feature.

class Product
  embeds_one :feature

  delegate :color, to: :feature, allow_nil: true
end

Problem

I am using ruby 2, rails 4, and mongoid-rails gem I have two models: ``` class Product embeds_one :feature end class Feature embedded_in :product field :color, type: String end ``` Lets say I have a product: ``` p = Product.new ``` I want to be able to call something like: ``` p.color = "blue" ``` instead of having to do: ``` p.feature.color = "blue" ``` the same goes for calling attributes: ``` p.color => "blue" ``` vs. the less ideal (and current situation) ``` p.feature.color => "blue" ``` I know with active records you can use delegations, but how would I set this up in mongoid without having to fill up my model with tons of methods referencing the feature model?

Original source