Comments on: Can’t dup NilClass… maybe try `unloadable`

By: Abdo

Abdo — Sun, 01 Aug 2010 09:22:52 +0000

I used Kris fix in the plugin init.rb and it fixed the problem and the “A copy of ApplicationController has been removed from the module tree but is still active!” has gone.
Thanks Kris & Daniel

By: Nathan Hyde

Nathan Hyde — Tue, 01 Jun 2010 18:56:46 +0000

Just wanted to add yet another method of addressing this issue (when all the others don’t seem to work for you). Credit goes to James Adam for pointing me in the right direction and the comments in this article.

See http://groups.google.com/group/rubyonrails-talk/browse_thread/thread/f54f18f4d4354926?pli=1 for an explanation.

In environment.rb:
Rails::Initializer.run do |config| # etc config.to_prepare do # use load to ensure the added functionality is actually evaluated every time load 'path/to/your/extension.rb' end end

By: Daniel X Moore

Daniel X Moore — Fri, 26 Mar 2010 17:50:58 +0000

Thanks Evan! That’s a better explanation and makes a lot of sense. I’ll try it that way the next time I encounter the issue.

By: Kris

Kris — Fri, 26 Mar 2010 13:44:27 +0000

@Fred – in my case the init.rb in my plugin as that is where I was getting the error. It maybe different if you are getting the error for your Rails app itself…

By: Evan Owen

Evan Owen — Wed, 24 Mar 2010 20:31:12 +0000

Actually, the real cause of this problem is that ActiveRecord also defines self.included, and since you’re not calling “super” inside your method, ActiveRecord never gets the call and can’t finish loading your model, causing the “can’t dup nil” errors when you try to call the association.

To fix this, simply do:

def self.included(account)
account.class_eval do
has_many :characters
end
super # fixes the “can’t dup nil” issue
end

By: xain

xain — Wed, 23 Dec 2009 15:20:10 +0000

I still get the problem, and I don’t know how to fix it. The solutions listed above cannot fix it. The only option I can choose now is to downgrade to rails 2.2.2

By: crackertime

crackertime — Sun, 20 Dec 2009 04:20:10 +0000

Snap this started happening today after I updated my XUbuntu system to the latest. I guess the process fudged my rails files. I am not using engines. Maybe it is because I have a model named User? What gives? I don’t want to go around putting some crazy ass line like unloadable in all my models. That is just stupid in my opinion.

By: Felix

Felix — Thu, 10 Dec 2009 12:21:51 +0000

@Brad: Ta, my messages were also caused by an unnecessary “require ‘user’” in a file in the lib folder. After removing the “require ‘user’” the problem went away. Another problem that went away when I did this was before_update being called twice in test mode (http://dev.rubyonrails.org/ticket/480).

By: Stefan

Stefan — Fri, 04 Dec 2009 12:35:40 +0000

thank you so much!
@Gary: I’m using 2.3.4 and I had the same problem.

By: @akorshkov

@akorshkov — Wed, 21 Oct 2009 14:11:07 +0000

Thanks, thanks, thanks!
Writing code is a pleasure again