CanCan: wrong number of arguments(1 for 0) - ruby-on-rails-3

Question

I can't seem to get CanCan working. This has turned out to be quite frustrating, especially when I have followed the rule book and tried, seemingly, all the tricks under the sun to get it to work.
I am using Rails 3.1.2, Devise 2.1.2, and CanCan 1.6.8. I set-up a separate role model as described by RyanB here.
This is my code.
1) ability.rb
class Ability
include CanCan::Ability
def initializer(user)
user ||= User.new # For users with no account
if (user.has_role?(:admin)) || (user.has_role?(:mod))
can :manage, :all
elsif user.has_role?(:registered)
can :read, :all
can :create, :all
can :update, Question do |question|
question.try(:user) == (user || user.has_role?(:admin) || user.has_role?(:mod))
end
can :destroy, Question do |question|
question.try(:user) == (user || user.has_role?(:admin) || user.has_role?(:mod))
end
else
can :read, :all
end
end
end
2) has_role? definition in user.rb
def has_role?(role_sym)
roles.any? { |r| r.name.underscore.to_sym == role_sym }
end
3) Controller before filters
before_filter :authenticate_user!, :except => :show
load_and_authorize_resource
skip_authorize_resource :only => :show
Authorizing any controller with CanCan results in the same error on all actions.
EDIT: Stack Trace
cancan (1.6.8) lib/cancan/controller_additions.rb:352:in `initialize'
cancan (1.6.8) lib/cancan/controller_additions.rb:352:in `new'
cancan (1.6.8) lib/cancan/controller_additions.rb:352:in `current_ability'
cancan (1.6.8) lib/cancan/controller_resource.rb:207:in `current_ability'
cancan (1.6.8) lib/cancan/controller_resource.rb:77:in `load_collection?'
cancan (1.6.8) lib/cancan/controller_resource.rb:33:in `load_resource'
cancan (1.6.8) lib/cancan/controller_resource.rb:25:in `load_and_authorize_resource'
cancan (1.6.8) lib/cancan/controller_resource.rb:10:in `block in add_before_filter'
activesupport (3.2.1) lib/active_support/callbacks.rb:429:in `_run__458654864__process_action__156152648__callbacks'
activesupport (3.2.1) lib/active_support/callbacks.rb:405:in `__run_callback'
activesupport (3.2.1) lib/active_support/callbacks.rb:385:in `_run_process_action_callbacks'
activesupport (3.2.1) lib/active_support/callbacks.rb:81:in `run_callbacks'
actionpack (3.2.1) lib/abstract_controller/callbacks.rb:17:in `process_action'
actionpack (3.2.1) lib/action_controller/metal/rescue.rb:29:in `process_action'
actionpack (3.2.1) lib/action_controller/metal/instrumentation.rb:30:in `block in process_action'
activesupport (3.2.1) lib/active_support/notifications.rb:123:in `block in instrument'
activesupport (3.2.1) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
activesupport (3.2.1) lib/active_support/notifications.rb:123:in `instrument'
actionpack (3.2.1) lib/action_controller/metal/instrumentation.rb:29:in `process_action'
actionpack (3.2.1) lib/action_controller/metal/params_wrapper.rb:205:in `process_action'
activerecord (3.2.1) lib/active_record/railties/controller_runtime.rb:18:in `process_action'
actionpack (3.2.1) lib/abstract_controller/base.rb:121:in `process'
actionpack (3.2.1) lib/abstract_controller/rendering.rb:45:in `process'
actionpack (3.2.1) lib/action_controller/metal.rb:203:in `dispatch'
actionpack (3.2.1) lib/action_controller/metal/rack_delegation.rb:14:in `dispatch'
actionpack (3.2.1) lib/action_controller/metal.rb:246:in `block in action'
actionpack (3.2.1) lib/action_dispatch/routing/route_set.rb:66:in `call'
actionpack (3.2.1) lib/action_dispatch/routing/route_set.rb:66:in `dispatch'
actionpack (3.2.1) lib/action_dispatch/routing/route_set.rb:30:in `call'
journey (1.0.4) lib/journey/router.rb:68:in `block in call'
journey (1.0.4) lib/journey/router.rb:56:in `each'
journey (1.0.4) lib/journey/router.rb:56:in `call'
actionpack (3.2.1) lib/action_dispatch/routing/route_set.rb:589:in `call'
warden (1.2.1) lib/warden/manager.rb:35:in `block in call'
warden (1.2.1) lib/warden/manager.rb:34:in `catch'
warden (1.2.1) lib/warden/manager.rb:34:in `call'
actionpack (3.2.1) lib/action_dispatch/middleware/best_standards_support.rb:17:in `call'
rack (1.4.1) lib/rack/etag.rb:23:in `call'
rack (1.4.1) lib/rack/conditionalget.rb:25:in `call'
actionpack (3.2.1) lib/action_dispatch/middleware/head.rb:14:in `call'
actionpack (3.2.1) lib/action_dispatch/middleware/params_parser.rb:21:in `call'
actionpack (3.2.1) lib/action_dispatch/middleware/flash.rb:242:in `call'
rack (1.4.1) lib/rack/session/abstract/id.rb:205:in `context'
rack (1.4.1) lib/rack/session/abstract/id.rb:200:in `call'
actionpack (3.2.1) lib/action_dispatch/middleware/cookies.rb:338:in `call'
activerecord (3.2.1) lib/active_record/query_cache.rb:64:in `call'
activerecord (3.2.1) lib/active_record/connection_adapters/abstract/connection_pool.rb:443:in `call'
actionpack (3.2.1) lib/action_dispatch/middleware/callbacks.rb:28:in `block in call'
activesupport (3.2.1) lib/active_support/callbacks.rb:405:in `_run__446710069__call__461654473__callbacks'
activesupport (3.2.1) lib/active_support/callbacks.rb:405:in `__run_callback'
activesupport (3.2.1) lib/active_support/callbacks.rb:385:in `_run_call_callbacks'
activesupport (3.2.1) lib/active_support/callbacks.rb:81:in `run_callbacks'
actionpack (3.2.1) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
actionpack (3.2.1) lib/action_dispatch/middleware/reloader.rb:65:in `call'
actionpack (3.2.1) lib/action_dispatch/middleware/remote_ip.rb:31:in `call'
actionpack (3.2.1) lib/action_dispatch/middleware/debug_exceptions.rb:16:in `call'
actionpack (3.2.1) lib/action_dispatch/middleware/show_exceptions.rb:56:in `call'
railties (3.2.1) lib/rails/rack/logger.rb:26:in `call_app'
railties (3.2.1) lib/rails/rack/logger.rb:16:in `call'
actionpack (3.2.1) lib/action_dispatch/middleware/request_id.rb:22:in `call'
rack (1.4.1) lib/rack/methodoverride.rb:21:in `call'
rack (1.4.1) lib/rack/runtime.rb:17:in `call'
activesupport (3.2.1) lib/active_support/cache/strategy/local_cache.rb:72:in `call'
rack (1.4.1) lib/rack/lock.rb:15:in `call'
actionpack (3.2.1) lib/action_dispatch/middleware/static.rb:53:in `call'
railties (3.2.1) lib/rails/engine.rb:479:in `call'
railties (3.2.1) lib/rails/application.rb:220:in `call'
rack (1.4.1) lib/rack/content_length.rb:14:in `call'
railties (3.2.1) lib/rails/rack/log_tailer.rb:14:in `call'
rack (1.4.1) lib/rack/handler/webrick.rb:59:in `service'
/home/administrator/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/webrick/httpserver.rb:138:in `service'
/home/administrator/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/webrick/httpserver.rb:94:in `run'
/home/administrator/.rvm/rubies/ruby-1
.9.3-p125/lib/ruby/1.9.1/webrick/server.rb:191:in `block in start_thread'

Answer 1

Okay, it seems, I did not followed ALL the rules of the rule book. Although I cannot see how this could be a problem. To get this working, I deleted my ability.rb file that I created manually, and used the rails g cancan:ability command to generate the same file in the same directory, and used the same code. And now it works like a charm.