如何在Ruby on Rails中从Gem向现有模型添加多态关联？

Question

Suppose I have included a gem called acts_as_locatable in my project with an ActsAsLocatable::Location class defined within it. I want to add a polymorphic :subject association to this class, which could be accomplished by simply editing the class in the gem to add the association, like this:

module ActsAsLocatable

  class Location < ::ApplicationRecord

    belongs_to :subject, polymorphic: true

    ...

  end

end

But this is a bad idea since I don't want to have to maintain this change with each update of the gem. Forking the Gem and modifying the fork also suffers from this same problem.

How can I extend, decorate or otherwise augment this class to add a polymorphic :subject association without editing the model file in the gem, while leaving the rest of the functionality of the gem undisturbed?

Answer 1

After doing a bit more research about monkey patching, it seems that one solution is to add an initializer (such as <root>/config/initializers/acts_as_locatable.rb ):

ActsAsLocatable::Location.class_eval do
  belongs_to      :subject,           polymorphic: true
end

Is this the best option?