运行时出现以下错误：
bundle exec rake db:migrate
我明白了：
耙子流产了！ StandardError：发生错误，此错误以及稍后发生 迁移已取消：undefined method `[]' for nil:NilClass Tasks: TOP => db:migrate (See full trace by running task with --trace)
有什么想法来解决这个问题？这是一个带有一次迁移的新应用程序。
跟踪：
C:\Sites\check>bundle exec rake db:migrate --trace
** Invoke db:migrate (first_time)
** Invoke environment (first_time)
** Execute environment
** Invoke db:load_config (first_time)
** Execute db:load_config
** Execute db:migrate
== Checklist: migrating ======================================================
-- create_table(:launch_checklists)
-> 0.1650s
== Checklist: migrated (0.1690s) =============================================
rake aborted!
StandardError: An error has occurred, this and all later migrations canceled:
undefined method `[]' for nil:NilClassC:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/
1.9.1/gems/activerecord-4.0.2/lib/active_record/attribute_methods/read.rb:86:in
`block in read_attribute'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/attribute_methods/read.rb:84:in `fetch'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/attribute_methods/read.rb:84:in `read_attribute'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/attribute_methods.rb:243:in `block in attributes'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/attribute_methods.rb:242:in `each'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/attribute_methods.rb:242:in `each_with_object'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/attribute_methods.rb:242:in `attributes'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/attribute_methods/dirty.rb:84:in `keys_for_partial_write'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/attribute_methods/dirty.rb:78:in `create_record'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/callbacks.rb:306:in `block in create_record'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activesupport-4.0.2/lib/act
ive_support/callbacks.rb:373:in `_run__124220591__create__callbacks'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activesupport-4.0.2/lib/act
ive_support/callbacks.rb:80:in `run_callbacks'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/callbacks.rb:306:in `create_record'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/timestamp.rb:57:in `create_record'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/persistence.rb:477:in `create_or_update'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/callbacks.rb:302:in `block in create_or_update'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activesupport-4.0.2/lib/act
ive_support/callbacks.rb:373:in `_run__124220591__save__callbacks'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activesupport-4.0.2/lib/act
ive_support/callbacks.rb:80:in `run_callbacks'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/callbacks.rb:302:in `create_or_update'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/persistence.rb:128:in `save!'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/validations.rb:57:in `save!'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/attribute_methods/dirty.rb:41:in `save!'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/transactions.rb:275:in `block in save!'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/transactions.rb:326:in `block in with_transaction_returning_status'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/connection_adapters/abstract/database_statements.rb:200:in `transactio
n'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/transactions.rb:209:in `transaction'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/transactions.rb:323:in `with_transaction_returning_status'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/transactions.rb:275:in `save!'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/protected_attributes-1.0.3/
lib/active_record/mass_assignment_security/validations.rb:17:in `create!'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/migration.rb:990:in `record_version_state_after_migrating'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/migration.rb:960:in `block in execute_migration_in_transaction'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/migration.rb:1005:in `block in ddl_transaction'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/connection_adapters/abstract/database_statements.rb:202:in `block in t
ransaction'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/connection_adapters/abstract/database_statements.rb:210:in `within_new
_transaction'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/connection_adapters/abstract/database_statements.rb:202:in `transactio
n'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/transactions.rb:209:in `transaction'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/migration.rb:1005:in `ddl_transaction'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/migration.rb:958:in `execute_migration_in_transaction'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/migration.rb:920:in `block in migrate'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/migration.rb:916:in `each'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/migration.rb:916:in `migrate'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/migration.rb:764:in `up'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/migration.rb:742:in `migrate'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activerecord-4.0.2/lib/acti
ve_record/railties/databases.rake:42:in `block (2 levels) in <top (required)>'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/rake-10.3.2/lib/rake/task.r
b:240:in `call'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/rake-10.3.2/lib/rake/task.r
b:240:in `block in execute'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/rake-10.3.2/lib/rake/task.r
b:235:in `each'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/rake-10.3.2/lib/rake/task.r
b:235:in `execute'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/rake-10.3.2/lib/rake/task.r
b:179:in `block in invoke_with_call_chain'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/1.9.1/monitor.rb:211:in `mon_synchronize'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/rake-10.3.2/lib/rake/task.r
b:172:in `invoke_with_call_chain'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/rake-10.3.2/lib/rake/task.r
b:165:in `invoke'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/rake-10.3.2/lib/rake/applic
ation.rb:150:in `invoke_task'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/rake-10.3.2/lib/rake/applic
ation.rb:106:in `block (2 levels) in top_level'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/rake-10.3.2/lib/rake/applic
ation.rb:106:in `each'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/rake-10.3.2/lib/rake/applic
ation.rb:106:in `block in top_level'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/rake-10.3.2/lib/rake/applic
ation.rb:115:in `run_with_threads'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/rake-10.3.2/lib/rake/applic
ation.rb:100:in `top_level'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/rake-10.3.2/lib/rake/applic
ation.rb:78:in `block in run'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/rake-10.3.2/lib/rake/applic
ation.rb:176:in `standard_exception_handling'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/rake-10.3.2/lib/rake/applic
ation.rb:75:in `run'
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/rake-10.3.2/bin/rake:33:in
`<top (required)>'
C:/RailsInstaller/Ruby1.9.3/bin/rake:23:in `load'
C:/RailsInstaller/Ruby1.9.3/bin/rake:23:in `<main>'
Tasks: TOP => db:migrate
的database.yml
development:
adapter: postgresql
database: check_development
encoding: utf8
pool: 5
timeout: 5000
host: localhost
port: 5432
username: postgres
password: mypass
test:
adapter: postgresql
database: check_test
encoding: utf8
pool: 5
timeout: 5000
host: localhost
port: 5432
username: postgres
password: mypass
production:
adapter: postgresql
database: check_production
encoding: utf8
pool: 5
timeout: 5000
host: localhost
port: 5432
username: postgres
password: mypass