Ruby-on-rails 在“引用”迁移中指定列名

Specifying column name in a "references" migration

提问by caarlos0

I want to make a migrationin Rails, referencing another table. Usually, I would do something like:

我想migration在 Rails 中创建一个，引用另一个表。通常，我会这样做：

add_column :post, :user, :references

This creates a column named user_idin poststable. But what if, instead of user_id, I want something like author_id? How can I do that?

这将创建一个名为列user_id在posts表中。但是如果，而不是user_id，我想要类似的东西author_id呢？我怎样才能做到这一点？

采纳答案by mschultz

Do it manually:

手动执行：

add_column :post, :author_id, :integer

but now, when you create the belongs_to statement, you will have to modify it, so now you have to call

但是现在，当你创建belongs_to 语句时，你将不得不修改它，所以现在你必须调用

def post
    belongs_to :user, :foreign_key => 'author_id'
end

回答by ecoologic

In Rails 4.2+you can also set foreign keysin the db as well, which is a great idea.

在Rails 4.2+ 中，您还可以在 db 中设置外键，这是一个好主意。

For simple associations this can be done also on t.referencesadding foreign_key: true, but in this case you'll need two lines.

对于简单的关联，这也可以通过t.references添加来完成foreign_key: true，但在这种情况下，您需要两行。

# The migration
add_reference :posts, :author, index: true
add_foreign_key :posts, :users, column: :author_id

# The model
belongs_to :author, class_name: "User"

回答by Sheharyar

For Rails 5+

对于 Rails 5+

Initial Definition:

初始定义：

If you are defining your Postmodel table, you can set references, indexand foreign_keyin one line:

如果您正在定义Post模型表，则可以在一行中设置references,index和foreign_key：

t.references :author, index: true, foreign_key: { to_table: :users }

---

---

Update Existing:

更新现有：

If you are adding references to an existing table, you can do this:

如果要添加对现有表的引用，可以执行以下操作：

add_reference :posts, :author, foreign_key: { to_table: :users }

---

---

^{Note:The default value for indexis true.}

^{注意：默认值为indextrue。}

回答by nathanvda

In rails 4, when using postgresql and the schema_plusgem you can just write

在 rails 4 中，当使用 postgresql 和schema_plusgem 时，你可以只写

add_reference :posts, :author, references: :users

This will create a column author_id, which correctly refers to users(id).

这将创建一个列author_id，它正确地引用users(id).

And in your model, you write

在你的模型中，你写

belongs_to :author, class_name: "User"

Note, when creating a new table you can write it as follows:

请注意，在创建新表时，您可以按如下方式编写：

create_table :things do |t| 
  t.belongs_to :author, references: :users 
end 

Note: the schema_plusgem in it's entirety is not compatible with rails 5+, but this functionality is offered by the gem schema_auto_foreign_keys(part of schema_plus) which is compatible with rails 5.

注意：整个schema_plusgem 与 rails 5+ 不兼容，但此功能由与 rails 5 兼容的 gem schema_auto_foreign_keys（schema_plus 的一部分）提供。

回答by jes5199

If you aren't using a foreign key, then it doesn't matter what the actual table name of the other table is.

如果您没有使用外键，那么另一个表的实际表名是什么并不重要。

add_reference :posts, :author

As of Rails 5, if you're using a foreign key, you can specify the name of the other table in the foreign key options. (see https://github.com/rails/rails/issues/21563for discussion)

从 Rails 5 开始，如果您使用外键，则可以在外键选项中指定另一个表的名称。（讨论见https://github.com/rails/rails/issues/21563）

add_reference :posts, :author, foreign_key: {to_table: :users}

Prior to Rails 5, you should add the foreign key as a separate step:

在 Rails 5 之前，您应该添加外键作为单独的步骤：

add_foreign_key :posts, :users, column: :author_id

回答by sekmo

alias_attribute(new_name, old_name)is very handy. Just create your model and the relationship:

alias_attribute(new_name, old_name)非常方便。只需创建您的模型和关系：

rails g model Post title user:references

then edit the model and add an attribute alias with

然后编辑模型并添加属性别名

alias_attribute :author, :user

After that you'll be able to run things like

之后，您将能够运行诸如

Post.new(title: 'My beautiful story', author: User.first)