Using record delegations with Mongoid Rails and Ruby

Question

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?

Answer 1

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