정의되지 않은 메소드 'to_sym'for nil : 마이그레이션 후 NilClass

Question

다음은 Rails 프로젝트에서 devise, cancan 및 rolify를 사용하여 Rolify Tutorial입니다. 새로운 마이그레이션을 생성 한 후 (잘 작동 함)이 오류가 발생합니다.

undefined method `to_sym' for nil:NilClass

내가 뭘 잘못하고 있는지 몰라. 이것은 제 디버그입니다.

사용자 테이블을 변경하기위한

내 이동은 다음과 같습니다

class AlterUsersTable1 < ActiveRecord::Migration 
    def up 
    change_table :users, :id => true do |t| 
     t.references :genre, :null => false, :default => 1 
     t.string :first_name, :null => false, :default => '' 
     t.string :last_name, :null => false, :default => '' 
     t.string :company, :null => true 
     t.boolean :status, :null => false, :default => true 
    end 

    execute <<-SQL 
    ALTER TABLE users 
    ADD CONSTRAINT fk_users_genre 
    FOREIGN KEY (genre_id) 
    REFERENCES genres(id) 
    SQL 

    execute <<-SQL 
    ALTER TABLE users 
    DROP PRIMARY KEY, ADD PRIMARY KEY (id, genre_id)  
    SQL 
end 

# RESET THE TABLE 
def down 
    execute <<-SQL 
    ALTER TABLE users 
    DROP FOREIGN KEY fk_users_genre 
    SQL 

    execute <<-SQL 
    ALTER TABLE users 
    DROP PRIMARY KEY, ADD PRIMARY KEY (id)  
    SQL 

    remove_column :users, :first_name 
    remove_column :users, :last_name 
    remove_column :users, :company 
    remove_column :users, :status 
    remove_column :users, :genre_id 
end 
end 

내 루트 파일은 다음과 같습니다

devise_for :users 
    resources :users 
    resources :categories 
    root :to => 'home#index' 

application_controller.rb

before_filter :authenticate_user! 

이 내 추적

activerecord (3.2.19) lib/active_record/sanitization.rb:60:in `block in expand_hash_conditions_for_aggregates' 
activerecord (3.2.19) lib/active_record/sanitization.rb:59:in `each' 
activerecord (3.2.19) lib/active_record/sanitization.rb:59:in `expand_hash_conditions_for_aggregates' 
activerecord (3.2.19) lib/active_record/relation/query_methods.rb:326:in `build_where' 
activerecord (3.2.19) lib/active_record/relation/query_methods.rb:136:in `where' 
activerecord (3.2.19) lib/active_record/querying.rb:9:in `where' 
orm_adapter (0.5.0) lib/orm_adapter/adapters/active_record.rb:17:in `get' 
devise (3.2.2) lib/devise/models/authenticatable.rb:208:in `serialize_from_session' 
devise (3.2.2) lib/devise.rb:462:in `block (2 levels) in configure_warden!' 
warden (1.2.3) lib/warden/session_serializer.rb:34:in `fetch' 
warden (1.2.3) lib/warden/proxy.rb:212:in `user' 
warden (1.2.3) lib/warden/proxy.rb:318:in `_perform_authentication' 
warden (1.2.3) lib/warden/proxy.rb:104:in `authenticate' 
warden (1.2.3) lib/warden/proxy.rb:114:in `authenticate?' 
devise (3.2.2) app/controllers/devise_controller.rb:103:in `require_no_authentication' 
activesupport (3.2.19) lib/active_support/callbacks.rb:407:in `_run__584588561542237872__process_action__1933424417154408597__callbacks' 
activesupport (3.2.19) lib/active_support/callbacks.rb:405:in `__run_callback' 
activesupport (3.2.19) lib/active_support/callbacks.rb:385:in `_run_process_action_callbacks' 
activesupport (3.2.19) lib/active_support/callbacks.rb:81:in `run_callbacks' 
actionpack (3.2.19) lib/abstract_controller/callbacks.rb:17:in `process_action' 
actionpack (3.2.19) lib/action_controller/metal/rescue.rb:29:in `process_action' 
actionpack (3.2.19) lib/action_controller/metal/instrumentation.rb:30:in `block in process_action' 
activesupport (3.2.19) lib/active_support/notifications.rb:123:in `block in instrument' 
activesupport (3.2.19) lib/active_support/notifications/instrumenter.rb:20:in `instrument' 
activesupport (3.2.19) lib/active_support/notifications.rb:123:in `instrument' 
actionpack (3.2.19) lib/action_controller/metal/instrumentation.rb:29:in `process_action' 
actionpack (3.2.19) lib/action_controller/metal/params_wrapper.rb:207:in `process_action' 
activerecord (3.2.19) lib/active_record/railties/controller_runtime.rb:18:in `process_action' 
actionpack (3.2.19) lib/abstract_controller/base.rb:121:in `process' 
actionpack (3.2.19) lib/abstract_controller/rendering.rb:45:in `process' 
actionpack (3.2.19) lib/action_controller/metal.rb:203:in `dispatch' 
actionpack (3.2.19) lib/action_controller/metal/rack_delegation.rb:14:in `dispatch' 
actionpack (3.2.19) lib/action_controller/metal.rb:246:in `block in action' 
actionpack (3.2.19) lib/action_dispatch/routing/route_set.rb:73:in `call' 
actionpack (3.2.19) lib/action_dispatch/routing/route_set.rb:73:in `dispatch' 
actionpack (3.2.19) lib/action_dispatch/routing/route_set.rb:36:in `call' 
actionpack (3.2.19) lib/action_dispatch/routing/mapper.rb:43: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 (3.2.19) lib/action_dispatch/routing/route_set.rb:608:in `call' 
warden (1.2.3) lib/warden/manager.rb:35:in `block in call' 
warden (1.2.3) lib/warden/manager.rb:34:in `catch' 
warden (1.2.3) lib/warden/manager.rb:34:in `call' 
actionpack (3.2.19) lib/action_dispatch/middleware/best_standards_support.rb:17:in `call' 
rack (1.4.5) lib/rack/etag.rb:23:in `call' 
rack (1.4.5) lib/rack/conditionalget.rb:25:in `call' 
actionpack (3.2.19) lib/action_dispatch/middleware/head.rb:14:in `call' 
actionpack (3.2.19) lib/action_dispatch/middleware/params_parser.rb:21:in `call' 
actionpack (3.2.19) lib/action_dispatch/middleware/flash.rb:242:in `call' 
rack (1.4.5) lib/rack/session/abstract/id.rb:210:in `context' 
rack (1.4.5) lib/rack/session/abstract/id.rb:205:in `call' 
actionpack (3.2.19) lib/action_dispatch/middleware/cookies.rb:341:in `call' 
activerecord (3.2.19) lib/active_record/query_cache.rb:64:in `call' 
activerecord (3.2.19) lib/active_record/connection_adapters/abstract/connection_pool.rb:479:in `call' 
actionpack (3.2.19) lib/action_dispatch/middleware/callbacks.rb:28:in `block in call' 
activesupport (3.2.19) lib/active_support/callbacks.rb:405:in `_run__3633975209017476260__call__1066395091297338092__callbacks' 
activesupport (3.2.19) lib/active_support/callbacks.rb:405:in `__run_callback' 
activesupport (3.2.19) lib/active_support/callbacks.rb:385:in `_run_call_callbacks' 
activesupport (3.2.19) lib/active_support/callbacks.rb:81:in `run_callbacks' 
actionpack (3.2.19) lib/action_dispatch/middleware/callbacks.rb:27:in `call' 
actionpack (3.2.19) lib/action_dispatch/middleware/reloader.rb:65:in `call' 
actionpack (3.2.19) lib/action_dispatch/middleware/remote_ip.rb:31:in `call' 
actionpack (3.2.19) lib/action_dispatch/middleware/debug_exceptions.rb:16:in `call' 
actionpack (3.2.19) lib/action_dispatch/middleware/show_exceptions.rb:56:in `call' 
railties (3.2.19) lib/rails/rack/logger.rb:32:in `call_app' 
railties (3.2.19) lib/rails/rack/logger.rb:16:in `block in call' 
activesupport (3.2.19) lib/active_support/tagged_logging.rb:22:in `tagged' 
railties (3.2.19) lib/rails/rack/logger.rb:16:in `call' 
actionpack (3.2.19) lib/action_dispatch/middleware/request_id.rb:22:in `call' 
rack (1.4.5) lib/rack/methodoverride.rb:21:in `call' 
rack (1.4.5) lib/rack/runtime.rb:17:in `call' 
activesupport (3.2.19) lib/active_support/cache/strategy/local_cache.rb:72:in `call' 
rack (1.4.5) lib/rack/lock.rb:15:in `call' 
actionpack (3.2.19) lib/action_dispatch/middleware/static.rb:63:in `call' 
railties (3.2.19) lib/rails/engine.rb:484:in `call' 
railties (3.2.19) lib/rails/application.rb:231:in `call' 
rack (1.4.5) lib/rack/content_length.rb:14:in `call' 
railties (3.2.19) lib/rails/rack/log_tailer.rb:17:in `call' 
rack (1.4.5) lib/rack/handler/webrick.rb:59:in `service' 
/Users/oscar/.rvm/rubies/ruby-1.9.3-p448/lib/ruby/1.9.1/webrick/httpserver.rb:138:in `service' 
/Users/oscar/.rvm/rubies/ruby-1.9.3-p448/lib/ruby/1.9.1/webrick/httpserver.rb:94:in `run' 
/Users/oscar/.rvm/rubies/ruby-1.9.3-p448/lib/ruby/1.9.1/webrick/server.rb:191:in `block in start_thread' 

Answer 1

OK, 나는 그러나이있다 :(

add_column :users, :genre_id, :integer, :default => 1, :null => false 
add_index :users, :genre_id