我的迁移问题非常烦人。
首先是错误消息：
bundle exec rake db:migrate --trace
(in /home/myhomefolder/msdnaa)
** Invoke db:migrate (first_time)
** Invoke environment (first_time)
** Execute environment
** Execute db:migrate
rake aborted!
An error has occurred, all later migrations canceled:
uninitialized constant Computers
现在我假设我们的某个管理员所做的更新是每次都发生这种情况的原因。即使根本没有迁移！
我所做的（除了在Stack Overflow上搜索解决方案之外）是grep每个文件的“Computers”。 当然有一些文件包含这个单词，我检查它们的语法错误和通常的东西，如缺少“：”。 然后我向同事请了一些帮助（他对红宝石的熟练程度比我高得多）并且他没有任何线索，一切看起来都正确。
我使用的是稍微旧版本的Ruby（1.8.7）和Rails（3.0.9），但我没有权利对我们的服务器进行更新，因此我必须处理它。 是的，我要求管理员对1.9.x和3.1.x进行更新，但这不是错误，因为它上周工作正常。 所以这是它应该工作的那些错误之一，但它没有，我打赌解决方案很容易就像喝水一样，但是我没有看到它！
有什么建议吗？
编辑：这是--trace：
/var/lib/gems/1.8/gems/activesupport-3.0.9/lib/active_support/inflector/meth ods.rb:113:in `constantize'
/var/lib/gems/1.8/gems/activesupport-3.0.9/lib/active_support/inflector/meth ods.rb:112:in `each'
/var/lib/gems/1.8/gems/activesupport-3.0.9/lib/active_support/inflector/meth ods.rb:112:in `constantize'
/var/lib/gems/1.8/gems/activesupport-3.0.9/lib/active_support/core_ext/strin g/inflections.rb:43:in `constantize'
/var/lib/gems/1.8/gems/activerecord-3.0.9/lib/active_record/migration.rb:407 :in `load_migration'
/var/lib/gems/1.8/gems/activerecord-3.0.9/lib/active_record/migration.rb:402 :in `migration'
/var/lib/gems/1.8/gems/activerecord-3.0.9/lib/active_record/migration.rb:397 :in `migrate'
/var/lib/gems/1.8/gems/activerecord-3.0.9/lib/active_record/migration.rb:539 :in `migrate'
/var/lib/gems/1.8/gems/activerecord-3.0.9/lib/active_record/migration.rb:615 :in `call'
/var/lib/gems/1.8/gems/activerecord-3.0.9/lib/active_record/migration.rb:615 :in `ddl_transaction'
/var/lib/gems/1.8/gems/activerecord-3.0.9/lib/active_record/migration.rb:538 :in `migrate'
/var/lib/gems/1.8/gems/activerecord-3.0.9/lib/active_record/migration.rb:525 :in `each'
/var/lib/gems/1.8/gems/activerecord-3.0.9/lib/active_record/migration.rb:525 :in `migrate'
/var/lib/gems/1.8/gems/activerecord-3.0.9/lib/active_record/migration.rb:435 :in `up'
/var/lib/gems/1.8/gems/activerecord-3.0.9/lib/active_record/migration.rb:417 :in `migrate'
/var/lib/gems/1.8/gems/activerecord-3.0.9/lib/active_record/railties/databas es.rake:142
/var/lib/gems/1.8/gems/rake-0.9.2/lib/rake/task.rb:205:in `call'
/var/lib/gems/1.8/gems/rake-0.9.2/lib/rake/task.rb:205:in `execute'
/var/lib/gems/1.8/gems/rake-0.9.2/lib/rake/task.rb:200:in `each'
/var/lib/gems/1.8/gems/rake-0.9.2/lib/rake/task.rb:200:in `execute'
/var/lib/gems/1.8/gems/rake-0.9.2/lib/rake/task.rb:158:in `invoke_with_call_ chain'
/usr/lib/ruby/1.8/monitor.rb:242:in `synchronize'
/var/lib/gems/1.8/gems/rake-0.9.2/lib/rake/task.rb:151:in `invoke_with_call_ chain'
/var/lib/gems/1.8/gems/rake-0.9.2/lib/rake/task.rb:144:in `invoke'
/var/lib/gems/1.8/gems/rake-0.9.2/lib/rake/application.rb:112:in `invoke_tas k'
/var/lib/gems/1.8/gems/rake-0.9.2/lib/rake/application.rb:90:in `top_level'
/var/lib/gems/1.8/gems/rake-0.9.2/lib/rake/application.rb:90:in `each'
/var/lib/gems/1.8/gems/rake-0.9.2/lib/rake/application.rb:90:in `top_level'
/var/lib/gems/1.8/gems/rake-0.9.2/lib/rake/application.rb:129:in `standard_e xception_handling'
/var/lib/gems/1.8/gems/rake-0.9.2/lib/rake/application.rb:84:in `top_level'
/var/lib/gems/1.8/gems/rake-0.9.2/lib/rake/application.rb:62:in `run'
/var/lib/gems/1.8/gems/rake-0.9.2/lib/rake/application.rb:129:in `standard_e xception_handling'
/var/lib/gems/1.8/gems/rake-0.9.2/lib/rake/application.rb:59:in `run'
/var/lib/gems/1.8/gems/rake-0.9.2/bin/rake:32
/var/lib/gems/1.8/bin/rake:19:in `load'
/var/lib/gems/1.8/bin/rake:19
Tasks: TOP => db:migrate
答案 0 :(得分：22)
我的猜测是你刚刚添加了一个名为20120221123456_computers.rb的迁移，在其中，你有类似的东西......
class SomeNameThatsNotComputers < ActiveRecord::Migration
...
当Rails执行迁移时，它期望执行定义类的文件，然后实例化该类，并在该类实例上调用#up或#down。 Rails如何知道要实例化的类？它应该与数字前缀和下划线后面的文件名部分对应，因此对于像20120221123456_computers.rb这样的文件名，类名必须是Computers。
答案 1 :(得分：0)
正如你所说，grep告诉“计算机”存在这就是问题所在。这意味着计算机未定义但已被使用。迁移首先加载应用程序环境，然后失败bcoz计算机未初始化