为什么create_association 不适用于belongs_to 关联？

Question

我有这个关联设置：

class Connection < ActiveRecord::Base
  belongs_to :membership
end

class Membership < ActiveRecord::Base
  has_many :connections, dependent: :destroy
end

但是，当我尝试执行以下操作时：

@membership ||= Membership.find_or_create_by(member: @member)
@connection ||= @membership.create_connection!(sent_at: Time.now, times_sent: 1, request_status: 0)

我收到此错误：

undefined method `create_connection!' for #<Membership:0x007fab2dac83b8>

尽管Rails API docs 说我应该能够做到这一点：

belongs_to(name, scope = nil, options = {}) Link

Methods will be added for retrieval and query for a single associated object, for which this object holds an id:

association is a placeholder for the symbol passed as the name argument, so belongs_to :author would add among others author.nil?.

create_association(attributes = {})
Returns a new object of the associated type that has been instantiated with attributes, linked to this object through a foreign key, and that has already been saved (if it passed the validation).

create_association!(attributes = {})
Does the same as create_association, but raises ActiveRecord::RecordInvalid if the record is invalid.

这可能是什么原因造成的？

Answer 1

我认为你们的关系有些混乱。您已链接 belongs_to 的文档。由于连接属于会员，您可以

@membership ||= @connection.create_membership(attr1: val1, attr2: val2)

但是，成员资格不属于连接。会员有许多联系。向下滚动到has_many，可以看到要建立关联，需要使用：

collection.create(attributes = {}, …)

将其应用于您的用例，您会得到

@connection || = @member.connections.create(sent_at: Time.now, times_sent: 1, request_status: 0)

Answer 2

我想通了，Rails 4 文档似乎已经过时了。

我应该做的是：

@membership.connections.create!(sent_at: Time.now, times_sent: 1, request_status: 0)

这对我有用。