我在调整数据库时遇到了一些问题，所以我去了之前的提交，但现在我运行时
rake db:drop
rake db:create
rake db:migrate
我收到错误：
rake aborted!
uninitialized constant User
/Users/Marcus/.rvm/gems/ruby-1.9.3-p448@rails3tutorial2ndEd/gems/activesupport-3.2.3/lib/active_support/inflector/methods.rb:229:in `block in constantize'
/Users/Marcus/.rvm/gems/ruby-1.9.3-p448@rails3tutorial2ndEd/gems/activesupport-3.2.3/lib/active_support/inflector/methods.rb:228:in `each'
/Users/Marcus/.rvm/gems/ruby-1.9.3-p448@rails3tutorial2ndEd/gems/activesupport-3.2.3/lib/active_support/inflector/methods.rb:228:in `constantize'
有关如何解决此问题的任何想法？