# Re: Overriding code from one engine with another (extending **URL:** \ **Category:** Engines\ **Created:** [October 10, 2006, 6:45am UTC](https://www.ruby-forum.com/t/re-overriding-code-from-one-engine-with-another-extending/71595 "2006-10-10T06:45:38Z")\ **Posts on this page:** 1\ **Page:** 1
**Author:** ![Brian\_Estlin](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/6f9a4e/32.png) [@Brian\_Estlin](https://www.ruby-forum.com/u/Brian_Estlin)\ **Post date:** [October 10, 2006, 6:45am UTC](https://www.ruby-forum.com/t/re-overriding-code-from-one-engine-with-another-extending/71595/1 "2006-10-10T06:45:38Z")
> Suppose I want to make an engine that builds on another > engine. Extending engine code is pretty trivial in the application - > but what about in another engine? I’m by no means an expert on engines, but I’ve been trying to do something similar and thought I’d share my experience. Specifically, I customized the UserEngine and LoginEngine in an application for my company, then realized I wanted the same customizations in more than one app. So I’ve been trying to make an Engine out of those customizations. And I think I’ve pretty much got it working. But not without some trouble. 1. Your application (not the plugin you’re creating) must not only load the plugins in the correct order in environment.rb, but must include the relevant modules in the right order in, say, ApplicationController (and ApplicationHelper if applicable). This is probably obvious to someone with more Engines experience, but it tripped me up for a while b/c I got weird errors, for example, my Permission class was defined but without any of the code from in UserEngine’s permission.rb. 2. Plugins might be loaded (or require’d) in other places. These have to be in order also. I ran into trouble trying to bootstrap the UserEngine because Permission.synchronize\_with\_controllers manually requires each controller class – it makes sure to require engines’ controllers before the app’s controllers, but doesn’t specify an order (other than filesystem order) to look at the various engines. (I hacked it so it would require LoginEngine’s controllers first, then UserEngine’s, then other engines). -Brian