Passing the argument of an action in link_to rails 3 - ruby-on-rails

Question

I have got an action which takes in an argument it goes like this :-
def join_as_student(course)
#course = course
.........
end
I have a route for this :-
resources :courses do
member do
get :join_as_student
end
end
I want to go to this route by clicking on the route like this :-
link_to "Join",join_as_student_course_path(:course => #course)
However this gives me error wrong number of arguments (0 for 1) in join_as_student action
How do I pass the argument of this action in the link_to ??
Update
Full stack of error : -
app/controllers/courses_controller.rb:23:in `join_as_student'
actionpack (3.1.3) lib/action_controller/metal/implicit_render.rb:4:in `send_action'
actionpack (3.1.3) lib/abstract_controller/base.rb:167:in `process_action'
actionpack (3.1.3) lib/action_controller/metal/rendering.rb:10:in `process_action'
actionpack (3.1.3) lib/abstract_controller/callbacks.rb:18:in `block in process_action'
activesupport (3.1.3) lib/active_support/callbacks.rb:425:in `_run__26464250__process_action__701751343__callbacks'
activesupport (3.1.3) lib/active_support/callbacks.rb:386:in `_run_process_action_callbacks'
activesupport (3.1.3) lib/active_support/callbacks.rb:81:in `run_callbacks'
actionpack (3.1.3) lib/abstract_controller/callbacks.rb:17:in `process_action'
actionpack (3.1.3) lib/action_controller/metal/rescue.rb:17:in `process_action'
actionpack (3.1.3) lib/action_controller/metal/instrumentation.rb:30:in `block in process_action'
activesupport (3.1.3) lib/active_support/notifications.rb:53:in `block in instrument'
activesupport (3.1.3) lib/active_support/notifications/instrumenter.rb:21:in `instrument'
activesupport (3.1.3) lib/active_support/notifications.rb:53:in `instrument'
actionpack (3.1.3) lib/action_controller/metal/instrumentation.rb:29:in `process_action'
actionpack (3.1.3) lib/action_controller/metal/params_wrapper.rb:201:in `process_action'
activerecord (3.1.3) lib/active_record/railties/controller_runtime.rb:18:in `process_action'
actionpack (3.1.3) lib/abstract_controller/base.rb:121:in `process'
actionpack (3.1.3) lib/abstract_controller/rendering.rb:45:in `process'
actionpack (3.1.3) lib/action_controller/metal.rb:193:in `dispatch'
actionpack (3.1.3) lib/action_controller/metal/rack_delegation.rb:14:in `dispatch'
actionpack (3.1.3) lib/action_controller/metal.rb:236:in `block in action'
actionpack (3.1.3) lib/action_dispatch/routing/route_set.rb:65:in `call'
actionpack (3.1.3) lib/action_dispatch/routing/route_set.rb:65:in `dispatch'
actionpack (3.1.3) lib/action_dispatch/routing/route_set.rb:29:in `call'
rack-mount (0.8.3) lib/rack/mount/route_set.rb:152:in `block in call'
rack-mount (0.8.3) lib/rack/mount/code_generation.rb:96:in `block in recognize'
rack-mount (0.8.3) lib/rack/mount/code_generation.rb:145:in `optimized_each'
rack-mount (0.8.3) lib/rack/mount/code_generation.rb:95:in `recognize'
rack-mount (0.8.3) lib/rack/mount/route_set.rb:141:in `call'
actionpack (3.1.3) lib/action_dispatch/routing/route_set.rb:532:in `call'
omniauth (1.0.3) lib/omniauth/strategy.rb:168:in `call!'
omniauth (1.0.3) lib/omniauth/strategy.rb:148:in `call'
sass (3.1.15) lib/sass/plugin/rack.rb:54:in `call'
client_side_validations (3.1.4) lib/client_side_validations/middleware.rb:18:in `call'
warden (1.1.1) lib/warden/manager.rb:35:in `block in call'
warden (1.1.1) lib/warden/manager.rb:34:in `catch'
warden (1.1.1) lib/warden/manager.rb:34:in `call'
actionpack (3.1.3) lib/action_dispatch/middleware/best_standards_support.rb:17:in `call'
rack (1.3.6) lib/rack/etag.rb:23:in `call'
rack (1.3.6) lib/rack/conditionalget.rb:25:in `call'
actionpack (3.1.3) lib/action_dispatch/middleware/head.rb:14:in `call'
actionpack (3.1.3) lib/action_dispatch/middleware/params_parser.rb:21:in `call'
actionpack (3.1.3) lib/action_dispatch/middleware/flash.rb:247:in `call'
rack (1.3.6) lib/rack/session/abstract/id.rb:195:in `context'
rack (1.3.6) lib/rack/session/abstract/id.rb:190:in `call'
actionpack (3.1.3) lib/action_dispatch/middleware/cookies.rb:331:in `call'
activerecord (3.1.3) lib/active_record/query_cache.rb:64:in `call'
activerecord (3.1.3) lib/active_record/connection_adapters/abstract/connection_pool.rb:477:in `call'
actionpack (3.1.3) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call'
activesupport (3.1.3) lib/active_support/callbacks.rb:392:in `_run_call_callbacks'
activesupport (3.1.3) lib/active_support/callbacks.rb:81:in `run_callbacks'
actionpack (3.1.3) lib/action_dispatch/middleware/callbacks.rb:28:in `call'
actionpack (3.1.3) lib/action_dispatch/middleware/reloader.rb:68:in `call'
rack (1.3.6) lib/rack/sendfile.rb:101:in `call'
actionpack (3.1.3) lib/action_dispatch/middleware/remote_ip.rb:48:in `call'
actionpack (3.1.3) lib/action_dispatch/middleware/show_exceptions.rb:47:in `call'
railties (3.1.3) lib/rails/rack/logger.rb:13:in `call'
rack (1.3.6) lib/rack/methodoverride.rb:24:in `call'
rack (1.3.6) lib/rack/runtime.rb:17:in `call'
activesupport (3.1.3) lib/active_support/cache/strategy/local_cache.rb:72:in `call'
rack (1.3.6) lib/rack/lock.rb:15:in `call'
actionpack (3.1.3) lib/action_dispatch/middleware/static.rb:53:in `call'
railties (3.1.3) lib/rails/engine.rb:456:in `call'
rack (1.3.6) lib/rack/content_length.rb:14:in `call'
railties (3.1.3) lib/rails/rack/log_tailer.rb:14:in `call'
rack (1.3.6) lib/rack/handler/webrick.rb:59:in `service'
/usr/local/ruby/lib/ruby/1.9.1/webrick/httpserver.rb:111:in `service'
/usr/local/ruby/lib/ruby/1.9.1/webrick/httpserver.rb:70:in `run'
/usr/local/ruby/lib/ruby/1.9.1/webrick/server.rb:183:in `block in start_thread
'
Thanks

Answer 1

Sorry, I missed. You can't pass params for action. use
link_to "Join",join_as_student_course_path(#course)
and
def join_as_student
#course = Course.find params[:id]
.........
end

Answer 2

Try
link_to "Join",join_as_student_course_path(#course)