Question

我正在尝试在我的rails 4 app中使用mailboxer。当我尝试部署数据库时出现问题。创建邮箱会话表时出错，该表在通知表中具有依赖关系。

我正在尝试删除通知对话的外键。

我创建了一个迁移说：

change_table :notifications do |t|
t.remove_foreign_key :conversations

然而，rake中止并说外键不存在。

rake aborted!
An error has occurred, this and all later migrations canceled:

PG::UndefinedObject: ERROR:  constraint "notifications_conversation_id_fk" of relation      "notifications" does not exist

我的架构包括： add_foreign_key＆＃34;通知＆＃34;，＆＃34;对话＆＃34;，名称：＆＃34; notifications_on_conversation_id＆＃34;

我尝试使用db：migrate：down创建邮箱的原始迁移，但也收到错误，说找不到＆＃39;命令＆＃39;。

有人可以帮忙吗？谢谢。

Answer 1

# Removes the given foreign key from the table.
# Removes the foreign key on +accounts.branch_id+.
remove_foreign_key :accounts, :branches

# Removes the foreign key on +accounts.owner_id+.
remove_foreign_key :accounts, column: :owner_id

# Removes the foreign key named +special_fk_name+ on the +accounts+ table.
remove_foreign_key :accounts, name: :special_fk_name

官方文件：http://api.rubyonrails.org/v4.2/classes/ActiveRecord/ConnectionAdapters/SchemaStatements.html#method-i-remove_foreign_key

Answer 2

架构中的add_foreign_key命令为外键指定了名称notifications_on_conversation_id。此名称与外国人通常根据列名称notifications_conversation_id_fk分配的默认名称不同。因此，您的remove_foreign_key命令必须指定现有的外键名称而不是列名称。尝试：

remove_foreign_key :notifications, name: "notifications_on_conversation_id"

Answer 3

当我跑步时我得到了：

 NoMethodError: undefined method `remove_foreign_key' for #<ActiveRecord::ConnectionAdapters::Table:0x00007faa35e94aa8>
Did you mean?  remove_index

智慧的话语-切勿将ID整数用作外键。我在假冒应用程序上练习时使用了标题参数，它导致：

ActiveRecord::AssociationTypeMismatch (Company(#70210936585940) expected, got "Company4" which is an instance of String(#70210933923380))

外国人 - 删除外键

3 个答案: