从引擎扩展rails类

Question

I'm playing around with creating a simple plugin system for my app. Currently, i wan't to be able to extend my activerecord models from inside the engine files.

Let's say i have a following model:

# /my_app/app/models/post.rb
class Post < ActiveRecord::Base
end

What i want to achieve is to be able to put a file, for example, /my_app/example_engine/app/example_engine/models/post.rb which will add some methods to my Post class. I was trying to make that by putting a following content to that file:

# /my_app/example_engine/app/example_engine/models/post.rb
Post.class_eval do
  def new_method
    "hello"
  end
end

But it seems that it's not a proper way of doing this cause it's not working. I probably lack some elementary knowledge about ruby classes or how rails works so i would be really thankful if anyone could help me with that.

Thanks in advance!

Answer 1

If you are ok with subclassing, I would recommend doing the following

Have your engine extend the base class under a namespace such as

    module MyEngine
      class Post < Post
        .....
      end
    end

No need to eval, just inherit from the base class and extend it as you need.