NameError: uninitialized constant ActionController::Dispatcher

问题

Found a similar post here but I am running a Mac so the first solution does not exactly apply and the second didn't work for me.

Running Mac OS 10.7.2, Xcode 4.2.1, rvm 1.10.1 using ruby 1.9.3p0 (2011-10-30 revision 33570) [x86_64-darwin11.2.0]

I believe the issue to due with rvm, however I do not know how to fix it

$ rails new dispatch_me
$ rails generate controller demo index 
$ rails console
Loading development environment (Rails 3.2.0.rc2)
1.9.3-p0 :001 > env = {}
 => {} 
1.9.3-p0 :002 > env['REQUEST_METHOD'] = 'GET'
 => "GET" 
1.9.3-p0 :003 > env['PATH_INFO'] = '/demo/index'
 => "/demo/index" 
1.9.3-p0 :004 > env['rack.input'] = StringIO.new
 => #<StringIO:0x007f946db0ece0> 
1.9.3-p0 :005 > ActionController::Dispatcher.new.call(env).last.body
NameError: uninitialized constant ActionController::Dispatcher
from (irb):5
from /Users/rudolph9/.rvm/gems/ruby-1.9.3-p0/gems/railties-3.2.0.rc2/lib/rails/commands/console.rb:47:in `start'
from /Users/rudolph9/.rvm/gems/ruby-1.9.3-p0/gems/railties-3.2.0.rc2/lib/rails/commands/console.rb:8:in `start'
from /Users/rudolph9/.rvm/gems/ruby-1.9.3-p0/gems/railties-    3.2.0.rc2/lib/rails/commands.rb:41:in `<top (required)>'
from script/rails:6:in `require'
from script/rails:6:in `<main>'
1.9.3-p0 :006 > 

I am following with the The Rails 3 Way

Again, I believe the issue to due with rvm, however I do not know how to fix it?

UPDATE: Maybe it doesn't have something to do with rvm, running native Ruby 1.8.7 and Rails 3.1.3 I run into the same issue:

>> ActionController::Dispatcher.new.call(env).last.body
NameError: uninitialized constant ActionController::Dispatcher
    from (irb):6

回答1:

Take a look at config.ru, in my case it is:

> cat config.ru 
# This file is used by Rack-based servers to start the application.

require ::File.expand_path('../config/environment',  __FILE__)
run Wagn::Application

The file was generated for 3.0 with Main::Application and it was changed for our local name.

I used this for my app (Rack::Test):

def app
  Wagn::Application
end

Note there is no '.new', since this class is an application, not a middleware.

回答2:

It looks ActionController::Dispatcher just doesn't exist in the version of rails you're using. If your following a book it's usually best to stick with the version of Rails the book was written for.

来源：https://stackoverflow.com/questions/8859409/nameerror-uninitialized-constant-actioncontrollerdispatcher