rails g gives uninitialized constant Rack::Mongoid

I get this error when I run 'rails g' (my app seems to run fine otherwise though, but I need to use a generator):

      /home/love/mongodb.roger/.bundler/ruby/1.8/gems/activesupport-3.0.9/lib/active_support/inflector/methods.rb:113:in `constantize': uninitialized constant Rack::Mongoid (NameError)
           from /home/love/mongodb.roger/.bundler/ruby/1.8/gems/activesupport-3.0.9/lib/active_support/inflector/methods.rb:112:in `each'
           from /home/love/mongodb.roger/.bundler/ruby/1.8/gems/activesupport-3.0.9/lib/active_support/inflector/methods.rb:112:in `constantize'
           from /home/love/mongodb.roger/.bundler/ruby/1.8/gems/actionpack-3.0.9/lib/action_dispatch/middleware/stack.rb:14:in `klass'
           from /home/love/mongodb.roger/.bundler/ruby/1.8/gems/actionpack-3.0.9/lib/action_dispatch/middleware/stack.rb:33:in `build'
           from /home/love/mongodb.roger/.bundler/ruby/1.8/gems/actionpack-3.0.9/lib/action_dispatch/middleware/stack.rb:79:in `build'
           from /home/love/mongodb.roger/.bundler/ruby/1.8/gems/railties-3.0.9/lib/rails/application.rb:209:in `inject'
           from /home/love/mongodb.roger/.bundler/ruby/1.8/gems/actionpack-3.0.9/lib/action_dispatch/middleware/stack.rb:79:in `each'
           from /home/love/mongodb.roger/.bundler/ruby/1.8/gems/actionpack-3.0.9/lib/action_dispatch/middleware/stack.rb:79:in `inject'
           from /home/love/mongodb.roger/.bundler/ruby/1.8/gems/actionpack-3.0.9/lib/action_dispatch/middleware/stack.rb:79:in `build'
           from /home/love/mongodb.roger/.bundler/ruby/1.8/gems/railties-3.0.9/lib/rails/application.rb:162:in `build_middleware_stack'
           from /home/love/mongodb.roger/.bundler/ruby/1.8/gems/railties-3.0.9/lib/rails/application/finisher.rb:35
           from /home/love/mongodb.roger/.bundler/ruby/1.8/gems/railties-3.0.9/lib/rails/initializable.rb:25:in `instance_exec'
           from /home/love/mongodb.roger/.bundler/ruby/1.8/gems/railties-3.0.9/lib/rails/initializable.rb:25:in `run'
           from /home/love/mongodb.roger/.bundler/ruby/1.8/gems/railties-3.0.9/lib/rails/initializable.rb:50:in `run_initializers'
           from /home/love/mongodb.roger/.bundler/ruby/1.8/gems/railties-3.0.9/lib/rails/initializable.rb:49:in `each'
           from /home/love/mongodb.roger/.bundler/ruby/1.8/gems/railties-3.0.9/lib/rails/initializable.rb:49:in `run_initializers'
           from /home开发者_JAVA技巧/love/mongodb.roger/.bundler/ruby/1.8/gems/railties-3.0.9/lib/rails/application.rb:134:in `initialize!'
           from /home/love/mongodb.roger/.bundler/ruby/1.8/gems/railties-3.0.9/lib/rails/application.rb:77:in `send'
           from /home/love/mongodb.roger/.bundler/ruby/1.8/gems/railties-3.0.9/lib/rails/application.rb:77:in `method_missing'
           from /home/love/mongodb.roger/config/environment.rb:7
           from /home/love/mongodb.roger/.bundler/ruby/1.8/gems/railties-3.0.9/lib/rails/application.rb:103:in `require_environment!'
           from /home/love/mongodb.roger/.bundler/ruby/1.8/gems/railties-3.0.9/lib/rails/commands.rb:16
           from script/rails:6:in `require'
           from script/rails:6

I use 1.8.7 (but I also get this error when I use 1.9.x with RVM).

ruby -v 
ruby 1.8.7 (2010-08-16 patchlevel 302) [x86_64-linux] 

rails -v 
Rails 3.0.9 

cat Gemfile 
source 'http://rubygems.org' 
gem 'rails', '3.0.9' 
gem "mongoid", "~> 2.1.0" 
gem "bson_ext", "~> 1.3" 
gem "devise" #, :git=>"https://github.com/plataformatec/devise.git" 
gem "rails-footnotes", ">= 3.7", :group => :development 
gem "compass" 
gem 'SystemTimer' 
gem "oa-oauth", :require => "omniauth/oauth" 
gem "warden" 
gem 'formtastic', '~> 1.1.0' 
gem 'paperclip' 
gem 'jquery-rails' 
gem 'acts-as-taggable-on' 
gem "gmaps4rails" 
gem 'browser' 
gem 'apotomo', "~>1.1.0" 
gem 'sass' 
gem 'chunky_png' 
gem 'mongoid-paperclip' 

Does anyone have any idea ?

remove the line from your config/application.rb file:

require "mongoid/railtie"

I have seen this issue on migrating from Rails 3.0.7 to Rails 3.1.3 when using Mongoid. To fix the problem find you where are doing all your mongoid requires - for example - in config/application.rb

require 'mongoid/railtie'
require 'action_controller/railtie'
require 'action_mailer/railtie'
require 'active_resource/railtie'
require 'rails/test_unit/railtie'

... then add require 'rack/mongoid' just before this to give you...

require 'rack/mongoid' # TADA!
require 'mongoid/railtie'
require 'action_controller/railtie'
require 'action_mailer/railtie'
require 'active_resource/railtie'
require 'rails/test_unit/railtie'

This got the Rails console working for me as well (rails c)