脚手架后无法迁移数据库。2.2节Ruby on Rails教程Michael Hartl

Question

我正在阅读Hartl ruby on rails教程（第2.2节），而在迁移数据库时遇到了麻烦。一切似乎都正常，然后我运行rails generate scaffold User name:string email:string 之后，我尝试运行包exec rake db：migrate并收到以下错误消息：$ bundle exec rake db:migrate                                                                                 == 20141125234257 CreateUsers: migrating ======================================-- create_table(:users)   -> 0.0079s== 20141125234257 CreateUsers: migrated (0.0080s) =============================rake aborted!StandardError: An error has occurred, this and all later migrations canceled:wrong number of arguments (1 for 0)/usr/local/rvm/gems/ruby-2.1.4@rails4/gems/activerecord-4.2.0.beta4/lib/active_record/connection_adapters/abstract_adapter.rb:271:in `initialize'/usr/local/rvm/gems/ruby-2.1.4@rails4/gems/activerecord-4.2.0.beta4/lib/active_record/connection_adapters/abstract_adapter.rb:271:in `new'/usr/local/rvm/gems/ruby-2.1.4@rails4/gems/activerecord-4.2.0.beta4/lib/active_record/connection_adapters/abstract_adapter.rb:271:in `substitute_at'/usr/local/rvm/gems/ruby-2.1.4@rails4/gems/activerecord-4.2.0.beta4/lib/active_record/relation.rb:97:in `block in substitute_values'/usr/local/rvm/gems/ruby-2.1.4@rails4/gems/activerecord-4.2.0.beta4/lib/active_record/relation.rb:96:in `each'/usr/local/rvm/gems/ruby-2.1.4@rails4/gems/activerecord-4.2.0.beta4/lib/active_record/relation.rb:96:in `each_with_index'/usr/local/rvm/gems/ruby-2.1.4@rails4/gems/activerecord-4.2.0.beta4/lib/active_record/relation.rb:96:in `substitute_values'/usr/local/rvm/gems/ruby-2.1.4@rails4/gems/activerecord-4.2.0.beta4/lib/active_record/relation.rb:56:in `insert'/usr/local/rvm/gems/ruby-2.1.4@rails4/gems/activerecord-4.2.0.beta4/lib/active_record/persistence.rb:521:in `_create_record'/usr/local/rvm/gems/ruby-2.1.4@rails4/gems/activerecord-4.2.0.beta4/lib/active_record/counter_cache.rb:139:in `_create_record'Tasks: TOP => db:migrate(See full trace by running task with --trace)我尝试返回到较早的提交，然后再次运行所有内容，但收到相同的错误消息。我是否还应该添加其他文件来帮助解决此问题？

Answer 1

以上更改gemfile的解决方案。

 gem 'arel', '6.0.0.beta2'

我收到以下错误消息。

You have requested:arel = 6.0.0.beta2

The bundle currently has arel locked at 6.0.0.

Try running `bundle update arel`

后

bundle update arel    

有效

Answer 2

我已经解决了

rake db:reset

之后

rake db:migrate

工作了。