Expected X to define Y error

2007-03-09

I just got hit by this famous error again. And I am not the only one:

Now, I know I should put my patches where my mouth is. And that’s exactly what I’m trying to do here. My application is on the 1.2 branch, and I get this error if I have the Response Logger plugin loaded. Trying again with Edge Rails, I again get the error. If I try with WEBrick or Mongrel, same error. Loading the console produces the same error. Using Windows or Linux changes nothing: same error.

The exact backtrace is:



 1 $ ruby script\console

 2 Loading development environment.

 3 ./script/../config/../config/../vendor/rails/activerecord/lib/../../activesupport/lib/active_support/dependencies.rb:249:in `load_missing_constant’: Expected ./script/../config/../config/../vendor/plugins/response_logger/lib/response_logger.rb to define ResponseLogger (LoadError)

 4         from ./script/../config/../config/../vendor/rails/activerecord/lib/../../activesupport/lib/active_support/dependencies.rb:452:in `const_missing’

 5         from ./script/../config/../config/../vendor/rails/activerecord/lib/../../activesupport/lib/active_support/dependencies.rb:464:in `const_missing’

 6         from ./script/../config/../config/../vendor/rails/activerecord/lib/../../activesupport/lib/active_support/dependencies.rb:260:in `load_missing_constant’

 7         from ./script/../config/../config/../vendor/rails/activerecord/lib/../../activesupport/lib/active_support/dependencies.rb:452:in `const_missing’

 8         from ./script/../config/../config/../vendor/rails/activerecord/lib/../../activesupport/lib/active_support/dependencies.rb:260:in `load_missing_constant’

 9         from ./script/../config/../config/../vendor/rails/activerecord/lib/../../activesupport/lib/active_support/dependencies.rb:452:in `const_missing’

10         from ./script/../config/../config/../vendor/rails/activerecord/lib/../../activesupport/lib/active_support/dependencies.rb:260:in `load_missing_constant’

11         from ./script/../config/../config/../vendor/rails/activerecord/lib/../../activesupport/lib/active_support/dependencies.rb:468:in `const_missing’

12          … 14 levels…

13         from C:/ruby/lib/ruby/1.8/irb/init.rb:250:in `load_modules’

14         from C:/ruby/lib/ruby/1.8/irb/init.rb:21:in `setup’

15         from C:/ruby/lib/ruby/1.8/irb.rb:54:in `start’

16         from C:/ruby/bin/irb.bat:20

In this application, I am using Engines, along with LoginEngine. You really need the right version of Engines with the right version of Rails for things to work out well: Rails 1.2 requires Engines 1.2.

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Engine Generator

2005-12-21

This article is obsolete now that Rails 2.3 has Engines in core.

Jon Lim on the Rails mailing list just announced the release of Engines Generator.

From the documentation:

$ script/generate engine UploadEngine

Please enter the author’s name: Joe Smith

Please enter the author’s email: joe.smith@xyz.com


We can generate the following licenses automatically for you:

0) None

1) GPL

2) MIT

3) LGPL

Please select a license: 2

‘MIT’ selected

exists vendor/plugins

create vendor/plugins/upload_engine

create vendor/plugins/upload_engine/README

create vendor/plugins/upload_engine/init_engine.rb

create vendor/plugins/upload_engine/app

create vendor/plugins/upload_engine/app/models

create vendor/plugins/upload_engine/app/controllers

create vendor/plugins/upload_engine/app/helpers

create vendor/plugins/upload_engine/app/views

create vendor/plugins/upload_engine/db

create vendor/plugins/upload_engine/db/migrate

create vendor/plugins/upload_engine/lib

create vendor/plugins/upload_engine/lib/upload_engine.rb

create vendor/plugins/upload_engine/lib/upload_engine

create vendor/plugins/upload_engine/public

create vendor/plugins/upload_engine/public/javascripts

create vendor/plugins/upload_engine/public/javascripts/upload_engine.js

create vendor/plugins/upload_engine/public/stylesheets

create vendor/plugins/upload_engine/public/stylesheets/upload_engine.css

create vendor/plugins/upload_engine/tasks

create vendor/plugins/upload_engine/tasks/upload_engine.rake

create vendor/plugins/upload_engine/test

create vendor/plugins/upload_engine/test/test_helper.rb

create vendor/plugins/upload_engine/test/fixtures

create vendor/plugins/upload_engine/test/functional

create vendor/plugins/upload_engine/test/unit


$ mv app/models/upload.rb vendor/plugins/upload_engine/app/models

$ mv app/controllers/upload_controller.rb vendor/plugins/upload_engine/app/controllers

$ mv app/views/upload vendor/plugins/upload_engine/app/views

$ mv public/javascripts/upload_engine.js vendor/plugins/upload_engine/public/javascripts

$ mv public/stylesheets/upload_engine.css vendor/plugins/upload_engine/public/stylesheets

config/environment.rb


1 Engines.start :upload_engine




$ script/server

This is way cool. Great work, Jon !

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Rails Engine configuration woes

2005-11-03

This article is obsolete now that Rails 2.3 has Engines in core.

I learned a nice one today. If you use Rails Engines and you want to configure your environments differently, you can’t do this:

config/environments/development.rb


1 module LoginEngine

2   config :salt => ‘test’

3 end
config/environments/production.rb


1 module LoginEngine

2   config :salt => ‘a-long-and-complicated-salt’

3 end
config/environment.rb


1 Engines.start :login

If you do that, you’ll get the following backtrace:



 1 $ ruby script\server

 2 ./script/../config/../vendor/rails/railties/lib/initializer.rb:178:in

 3 `load_environment’: undefined method `config’ for

 4 Rails::Initializer::LoginEngine:Module (NoMethodError)

 5        from ./script/../config/../vendor/rails/railties/lib/initializer.rb:150:in `load_environment’

 6        from ./script/../config/../vendor/rails/railties/lib/initializer.rb:147:in `silence_warnings’

 7        from ./script/../config/../vendor/rails/railties/lib/initializer.rb:147:in `load_environment’

 8        from ./script/../config/../vendor/rails/railties/lib/initializer.rb:73:in `process’

 9        from ./script/../config/../vendor/rails/railties/lib/initializer.rb:36:in `send’

10        from ./script/../config/../vendor/rails/railties/lib/initializer.rb:36:in `run’

11        from ./script/../config/../config/environment.rb:10

12        from C:/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:21:in `require__’

13        from C:/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:21:in `require’

14        from ./script/../config/../vendor/rails/railties/lib/commands/server.rb:52

15        from C:/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:21:in `require__’

16        from C:/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:21:in `require’

17        from script/server:3

What is happening is that Rails loads the environment file before the Rails Engine plugin is initialized. The solution ? Do everything in config/environment.rb:

config/environment.rb


 1 module LoginEngine

 2   case RAILS_ENV

 3   when ‘development’, ‘test’

 4     config :salt, "test"

 5   when ‘production’

 6     config :salt, "another-long-and-complicated-salt"

 7   end

 8 end

 9 

10 Engines.start :login

11

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Rails Engine Released

2005-11-01

This article is obsolete now that Rails 2.3 has Engines in core.

Over on the Rails mailing list, James Adams reports the initial release of Rails Engines.

What are engines ? They are plugins, more or less, except they also bundle controllers, views, partials, models and everything else you’d usually need in a component.

In fact, Rails Components could very well be implemented using Rails Engines.

I wonder how routes are handled. Can engines provide their own routes, or must the engine user define the routes he wants ? Gotta try that login_engine and see for myself.

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I am François Beausoleil, a Ruby on Rails and Scala developer. During the day, I work on Seevibes, a platform to measure social interactions related to TV shows. At night, I am interested many things. Read my biography.

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