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社区首页 >问答首页 >主动记录迁移从纯粹的伪装中失败？

问主动记录迁移从纯粹的伪装中失败？
EN

Stack Overflow用户
提问于 2012-01-25 02:22:18
回答 1查看 459关注 0票数 2

所以..。我有一个迁移(post.rb使用state_machine gem)

代码语言：javascript
复制
class AddVerifiedAtToPost < ActiveRecord::Migration
  def self.up

    add_column :posts, :verified_at, :datetime

    Post.find_each do |post|
      post.update_attribute(:verified_at, post.created_at) unless post.awaiting_verification?
    end

  end

  def self.down
    remove_column :posts, :verified_at
  end
end

..。这为nil类提供了一个未定义的方法“关系”...

所以我想--嗯，也许由于某种奇怪的原因，state_machine谓词方法在迁移上下文中不起作用，所以我修改了代码：

代码语言：javascript
复制
    Post.find_each do |post|
      post.update_attribute(:verified_at, post.created_at) unless post.status == "awaiting_verification"
    end

但随后我得到重复列"verified_at“已存在的错误......好的-然后我把我的add_column包装在一个column_exists中，给我一个迁移，现在看起来是这样的：

代码语言：javascript
复制
class AddVerifiedAtToPost < ActiveRecord::Migration
  def self.up

    unless column_exists?(:posts, :verified_at)
      add_column :posts, :verified_at, :datetime
    end

    Post.find_each do |post|
      post.update_attribute(:verified_at, post.created_at) unless post.status == "awaiting_verification"
    end

  end

  def self.down
    remove_column :posts, :verified_at
  end
end

..。运行rake :migrate...它成功了..万岁...但我仍然持怀疑态度，所以我运行rake :migrate:down VERSION=

然后再次运行rake :migrate，猜猜发生了什么？

代码语言：javascript
复制
==  AddVerifiedAtToPost: migrating ============================================
-- column_exists?(:posts, :verified_at)
   -> 0.0048s
-- add_column(:posts, :verified_at, :datetime)
   -> 0.0644s
rake aborted!
An error has occurred, all later migrations canceled:

undefined method `column' for nil:NilClass

(See full trace by running task with --trace)

..。我再次运行rake :migrate，它可以工作...我做了rake db:migrate:down，然后rake db:migrate--得到同样的错误......

所以我做了一个实验..我运行了rake :migrate:down，删除了列..跳入控制台并执行ActiveRecord::Migration.add_column(:posts，:verified_at，:datetime)

已运行迁移--没有错误..似乎出于某种原因，这个迁移文件上下文中的add_column对我来说是非常奇怪的。

这是堆栈跟踪：

代码语言：javascript
复制
** Invoke db:migrate (first_time)
** Invoke environment (first_time)
** Execute environment
** Execute db:migrate
==  AddVerifiedAtToPost: migrating ============================================
-- column_exists?(:posts, :verified_at)
   -> 0.0052s
-- add_column(:posts, :verified_at, :datetime)
   -> 0.0805s
rake aborted!
An error has occurred, all later migrations canceled:

undefined method `column' for nil:NilClass
/Users/patrick/.rvm/gems/ree-1.8.7-2011.03@myapp/gems/activesupport-3.0.7/lib/active_support/whiny_nil.rb:48:in `method_missing'
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/Users/patrick/.rvm/gems/ree-1.8.7-2011.03@myapp/gems/arel-2.0.10/lib/arel/visitors/visitor.rb:15:in `send'
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/Users/patrick/.rvm/gems/ree-1.8.7-2011.03@myapp/gems/arel-2.0.10/lib/arel/tree_manager.rb:20:in `to_sql'
/Users/patrick/.rvm/gems/ree-1.8.7-2011.03@myapp/gems/arel-2.0.10/lib/arel/crud.rb:20:in `update'
/Users/patrick/.rvm/gems/ree-1.8.7-2011.03@myapp/gems/activerecord-3.0.7/lib/active_record/persistence.rb:255:in `update'
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/Users/patrick/.rvm/gems/ree-1.8.7-2011.03@myapp/gems/state_machine-1.0.0/lib/state_machine/transition_collection.rb:63:in `catch'
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/Users/patrick/.rvm/gems/ree-1.8.7-2011.03@myapp/gems/activesupport-3.0.7/lib/active_support/callbacks.rb:315:in `_callback_around_268'
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/Users/patrick/.rvm/gems/ree-1.8.7-2011.03@myapp/gems/activerecord-3.0.7/lib/active_record/transactions.rb:290:in `with_transaction_returning_status'
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/Users/patrick/.rvm/gems/ree-1.8.7-2011.03@global/bin/rake:19

注意，我还注释掉了所有post模型的之前/之后保存/创建回调，看看这是如何触发它的，而不是……

ruby-on-rails
ruby-on-rails-3
EN

回答 1

Stack Overflow用户

回答已采纳

发布于 2012-01-25 19:34:17

修改栏目前调用"reset_column_information“

票数 3
EN
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：

https://stackoverflow.com/questions/8991964

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