active admin undefined method `[]' for nil:NilClass

im working with active admin i have collection_select or dropdown box that populates the packages and crews im just wondering i why this

undefined method `' for nil:NilClass` i dont know what happened but it run few days ago and tested it once but now it raises this error are there possible way to solve this?

def create    @package = Package.find(params[:package_crew][:package_id])    crew = Crew.find(params[:package_crew][:crew_id] )    @package_crew = @package.add_crew(crew.id)    if @package_crew.save       redirect_to {admin_package_crew_url}    end end thanks in advance more power to us all

i tried this

def create   #pid = params[:package_crew][:crew_id] if params[:package_crew]   pid,cid = 2 #tried nil,0..10   if params[:package_crew]      pid = params[:package_crew][:package_id]      cid = params[:package_crew][:crew_id]   end   @package = Package.find_by_id(pid)   crew = Crew.find_by_id(cid)   #@package = Package.find(params[:package_crew][:package_id])   #crew = Crew.find(params[:package_crew][:crew_id] )   @package_crew = @package.add_crew(crew.id)   if @package_crew.save      redirect_to {admin_package_crew_url}   end end

add_crew method

def add_crew(crew_id)     current_package = package_crews.find_by_crew_id(crew_id)     if current_package       current_package.quantity = current_package.quantity.to_i + 1     else       current_package = package_crews.build(:crew_id => crew_id)       current_package.price = current_package.crew.price     end       current_package   end moving parameters

{"utf8"=>"✓", "authenticity_token"=>"n4WZpQpES6mnSO12oGKV/MeoxAVvV9OmJQKfhcpnvQM=", "crew_for_package"=>{"package_id"=>"1", "crew_id"=>"1", "quantity"=>"1"}, "commit"=>"Create Package crew"} stack error

app/admin/package_crews.rb:35:in `create' actionpack (3.2.1) lib/action_controller/metal/implicit_render.rb:4:in `send_action' actionpack (3.2.1) lib/abstract_controller/base.rb:167:in `process_action' actionpack (3.2.1) lib/action_controller/metal/rendering.rb:10:in `process_action' actionpack (3.2.1) lib/abstract_controller/callbacks.rb:18:in `block in process_action' activesupport (3.2.1) lib/active_support/callbacks.rb:447:in `_run__304549499__process_action__775442107__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 (1.0.3) lib/journey/router.rb:68:in `block in call' journey (1.0.3) lib/journey/router.rb:56:in `each' journey (1.0.3) lib/journey/router.rb:56:in `call' actionpack (3.2.1) lib/action_dispatch/routing/route_set.rb:589:in `call' sass (3.1.15) lib/sass/plugin/rack.rb:54: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 (3.2.1) 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:35: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__1039351831__call__833288071__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' railties (3.2.1) lib/rails/railtie/configurable.rb:30:in `method_missing' /home/led/.passenger/standalone/3.0.11-x86-ruby1.9.3-linux-gcc4.6.3-1002/support/lib/phusion_passenger/rack/request_handler.rb:96:in `process_request' /home/led/.passenger/standalone/3.0.11-x86-ruby1.9.3-linux-gcc4.6.3-1002/support/lib/phusion_passenger/abstract_request_handler.rb:513:in `accept_and_process_next_request' /home/led/.passenger/standalone/3.0.11-x86-ruby1.9.3-linux-gcc4.6.3-1002/support/lib/phusion_passenger/abstract_request_handler.rb:274:in `main_loop' /home/led/.passenger/standalone/3.0.11-x86-ruby1.9.3-linux-gcc4.6.3-1002/support/lib/phusion_passenger/rack/application_spawner.rb:206:in `start_request_handler' /home/led/.passenger/standalone/3.0.11-x86-ruby1.9.3-linux-gcc4.6.3-1002/support/lib/phusion_passenger/rack/application_spawner.rb:171:in `block in handle_spawn_application' /home/led/.passenger/standalone/3.0.11-x86-ruby1.9.3-linux-gcc4.6.3-1002/support/lib/phusion_passenger/utils.rb:479:in `safe_fork' /home/led/.passenger/standalone/3.0.11-x86-ruby1.9.3-linux-gcc4.6.3-1002/support/lib/phusion_passenger/rack/application_spawner.rb:166:in `handle_spawn_application' /home/led/.passenger/standalone/3.0.11-x86-ruby1.9.3-linux-gcc4.6.3-1002/support/lib/phusion_passenger/abstract_server.rb:357:in `server_main_loop' /home/led/.passenger/standalone/3.0.11-x86-ruby1.9.3-linux-gcc4.6.3-1002/support/lib/phusion_passenger/abstract_server.rb:206:in `start_synchronously' /home/led/.passenger/standalone/3.0.11-x86-ruby1.9.3-linux-gcc4.6.3-1002/support/lib/phusion_passenger/abstract_server.rb:180:in `start' /home/led/.passenger/standalone/3.0.11-x86-ruby1.9.3-linux-gcc4.6.3-1002/support/lib/phusion_passenger/rack/application_spawner.rb:129:in `start' /home/led/.passenger/standalone/3.0.11-x86-ruby1.9.3-linux-gcc4.6.3-1002/support/lib/phusion_passenger/spawn_manager.rb:253:in `block (2 levels) in spawn_rack_application' /home/led/.passenger/standalone/3.0.11-x86-ruby1.9.3-linux-gcc4.6.3-1002/support/lib/phusion_passenger/abstract_server_collection.rb:132:in `lookup_or_add' /home/led/.passenger/standalone/3.0.11-x86-ruby1.9.3-linux-gcc4.6.3-1002/support/lib/phusion_passenger/spawn_manager.rb:246:in `block in spawn_rack_application' /home/led/.passenger/standalone/3.0.11-x86-ruby1.9.3-linux-gcc4.6.3-1002/support/lib/phusion_passenger/abstract_server_collection.rb:82:in `block in synchronize' <internal:prelude>:10:in `synchronize' /home/led/.passenger/standalone/3.0.11-x86-ruby1.9.3-linux-gcc4.6.3-1002/support/lib/phusion_passenger/abstract_server_collection.rb:79:in `synchronize' /home/led/.passenger/standalone/3.0.11-x86-ruby1.9.3-linux-gcc4.6.3-1002/support/lib/phusion_passenger/spawn_manager.rb:244:in `spawn_rack_application' /home/led/.passenger/standalone/3.0.11-x86-ruby1.9.3-linux-gcc4.6.3-1002/support/lib/phusion_passenger/spawn_manager.rb:137:in `spawn_application' /home/led/.passenger/standalone/3.0.11-x86-ruby1.9.3-linux-gcc4.6.3-1002/support/lib/phusion_passenger/spawn_manager.rb:275:in `handle_spawn_application' /home/led/.passenger/standalone/3.0.11-x86-ruby1.9.3-linux-gcc4.6.3-1002/support/lib/phusion_passenger/abstract_server.rb:357:in `server_main_loop' /home/led/.passenger/standalone/3.0.11-x86-ruby1.9.3-linux-gcc4.6.3-1002/support/lib/phusion_passenger/abstract_server.rb:206:in `start_synchronously' /home/led/.passenger/standalone/3.0.11-x86-ruby1.9.3-linux-gcc4.6.3-1002/support/helper-scripts/passenger-spawn-server:99:in `<main>'

i dont know if its ok to post a activeadmin problem here sorry if i posted a wrong question just wondering if there is a activeadmin expert here thanks

The error says that on line 35 you are calling on something that is nil. Please tell us which is line 35, that may make it easier to find the problem. First, however, have a look at the rails guide on debugging to get ideas on how to debug the code and work out what the problem is.

Colin