NoMethodError in Ruby on Rails calling Class Method from a controller - ruby-on-rails

Question

I'm just learning RoR and have run into my first real bug. Would really appreciate some guidance with it. I am up to the point of creating a user sign in/out feature for a site I am building which will be maintained through sessions. When the sign in form submits it goes to a sessions controller which calls the 'create' method. When it does this it displays this error:
NoMethodError in
SessionsController#create
You have a nil object when you didn't
expect it! You might have expected an
instance of ActiveRecord::Base. The
error occurred while evaluating nil.[]
Here's the code for the create method:
33 def create
34 user = User.authenticate(params[:session][:email],
35 params[:session][:password])
36 if user.nil?
37 flash.now[:error] = "Invalid email/password combination."
38 #title = "Sign in"
39 render 'new'
40 else
41 sign_in user
42 redirect_back_or user
43 end
44 end
The application trace says the error is at
app/controllers/sessions_controller.rb:34:in `create'
So the issue seems to be with the authenticate method. This is a class method defined for my user object. What's weird is that I tested the method in rails console and it works fine. Below is the full trace. Again would be very grateful for some help with this. Thanks you.
Trace:
app/controllers/sessions_controller.rb:34:in
create' actionpack (3.0.4)
lib/action_controller/metal/implicit_render.rb:4:in
send_action' actionpack (3.0.4)
lib/abstract_controller/base.rb:150:in
process_action' actionpack (3.0.4)
lib/action_controller/metal/rendering.rb:11:in
process_action' actionpack (3.0.4)
lib/abstract_controller/callbacks.rb:18:in
block in process_action'
activesupport (3.0.4)
lib/active_support/callbacks.rb:435:in
run_4224187041876590211__process_action_3718750575726612430_callbacks'
activesupport (3.0.4)
lib/active_support/callbacks.rb:409:in
_run_process_action_callbacks'
activesupport (3.0.4)
lib/active_support/callbacks.rb:93:in
run_callbacks' actionpack (3.0.4)
lib/abstract_controller/callbacks.rb:17:in
process_action' actionpack (3.0.4)
lib/action_controller/metal/instrumentation.rb:30:in
block in process_action'
activesupport (3.0.4)
lib/active_support/notifications.rb:52:in
block in instrument' activesupport
(3.0.4)
lib/active_support/notifications/instrumenter.rb:21:in
instrument' activesupport (3.0.4)
lib/active_support/notifications.rb:52:in
instrument' actionpack (3.0.4)
lib/action_controller/metal/instrumentation.rb:29:in
process_action' actionpack (3.0.4)
lib/action_controller/metal/rescue.rb:17:in
process_action' actionpack (3.0.4)
lib/abstract_controller/base.rb:119:in
process' actionpack (3.0.4)
lib/abstract_controller/rendering.rb:41:in
process' actionpack (3.0.4)
lib/action_controller/metal.rb:138:in
dispatch' actionpack (3.0.4)
lib/action_controller/metal/rack_delegation.rb:14:in
dispatch' actionpack (3.0.4)
lib/action_controller/metal.rb:178:in
block in action' actionpack (3.0.4)
lib/action_dispatch/routing/route_set.rb:62:in
call' actionpack (3.0.4)
lib/action_dispatch/routing/route_set.rb:62:in
dispatch' actionpack (3.0.4)
lib/action_dispatch/routing/route_set.rb:27:in
call' rack-mount (0.6.14)
lib/rack/mount/route_set.rb:148:in
block in call' rack-mount (0.6.14)
lib/rack/mount/code_generation.rb:93:in
block in recognize' rack-mount
(0.6.14)
lib/rack/mount/code_generation.rb:68:in
optimized_each' rack-mount (0.6.14)
lib/rack/mount/code_generation.rb:92:in
recognize' rack-mount (0.6.14)
lib/rack/mount/route_set.rb:139:in
call' actionpack (3.0.4)
lib/action_dispatch/routing/route_set.rb:492:in
call' actionpack (3.0.4)
lib/action_dispatch/middleware/best_standards_support.rb:17:in
call' actionpack (3.0.4)
lib/action_dispatch/middleware/head.rb:14:in
call' rack (1.2.2)
lib/rack/methodoverride.rb:24:in
call' actionpack (3.0.4)
lib/action_dispatch/middleware/params_parser.rb:21:in
call' actionpack (3.0.4)
lib/action_dispatch/middleware/flash.rb:182:in
call' actionpack (3.0.4)
lib/action_dispatch/middleware/session/abstract_store.rb:149:in
call' actionpack (3.0.4)
lib/action_dispatch/middleware/cookies.rb:302:incall' activerecord (3.0.4)
lib/active_record/query_cache.rb:32:in
block in call' activerecord (3.0.4)
lib/active_record/connection_adapters/abstract/query_cache.rb:28:in
cache' activerecord (3.0.4)
lib/active_record/query_cache.rb:12:in
cache' activerecord (3.0.4)
lib/active_record/query_cache.rb:31:in
call' activerecord (3.0.4)
lib/active_record/connection_adapters/abstract/connection_pool.rb:354:in
call' actionpack (3.0.4)
lib/action_dispatch/middleware/callbacks.rb:46:in
block in call' activesupport (3.0.4)
lib/active_support/callbacks.rb:415:in
_run_call_callbacks' actionpack
(3.0.4)
lib/action_dispatch/middleware/callbacks.rb:44:in
call' rack (1.2.2)
lib/rack/sendfile.rb:107:in call'
actionpack (3.0.4)
lib/action_dispatch/middleware/remote_ip.rb:48:in
call' actionpack (3.0.4)
lib/action_dispatch/middleware/show_exceptions.rb:47:in
call' railties (3.0.4)
lib/rails/rack/logger.rb:13:incall'
rack (1.2.2) lib/rack/runtime.rb:17:in
call' activesupport (3.0.4)
lib/active_support/cache/strategy/local_cache.rb:72:in
call' rack (1.2.2)
lib/rack/lock.rb:11:in block in call'
<internal:prelude>:10:insynchronize'
rack (1.2.2) lib/rack/lock.rb:11:in
call' actionpack (3.0.4)
lib/action_dispatch/middleware/static.rb:30:in
call' railties (3.0.4)
lib/rails/application.rb:168:in call'
railties (3.0.4)
lib/rails/application.rb:77:in
method_missing' railties (3.0.4)
lib/rails/rack/log_tailer.rb:14:in
call' rack (1.2.2)
lib/rack/content_length.rb:13:in
call' rack (1.2.2)
lib/rack/handler/webrick.rb:52:in
service'
/Users/USERNAME_REMOVED/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/1.9.1/webrick/httpserver.rb:111:in
service'
/Users/USERNAME_REMOVED/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/1.9.1/webrick/httpserver.rb:70:in
run'
/Users/USERNAME_REMOVED/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/1.9.1/webrick/server.rb:183:in
block in start_thread'

Answer 1

params[:session] doesn't exist
def create
user = User.authenticate(params[:session][:email],
params[:session][:password]) if params[:session]
...

Answer 2

Instead of declaring method authenticate in class << self :
class << self
def authenticate(email, submitted_password)
user = find_by_email(email)
(user && user.has_password?(submitted_password)) ? user : nil
end
end
Try this: def self.authenticate(email, submitted_password). Be careful, you have to declare it out of class << self
In this case you are declaring a class method authenticate and you should able to call it in your controller, in the create method.