由多个属性的Rails find_or_create？ [英] Rails find_or_create by more than one attribute?

问题描述

有一个方便的动态属性在主动记录称为find_or_create_by：

There is a handy dynamic attribute in active-record called find_or_create_by:

Model.find_or_create_by_＆LT;属性＆GT;（：＆LT;属性＆GT; =＆gt;中）

但是，如果我需要不止一个属性find_or_create？

But what if I need to find_or_create by more than one attribute?

说我有一个模型来处理M：组和成员M-M间的关系称为GroupMember。我可能有很多情况下member_id = 4，但我再也不要超过一次实例，其中member_id = 4和GROUP_ID = 7。我试图找出是否有可能做这样的事情：

Say I have a model to handle a M:M relationship between Group and Member called GroupMember. I could have many instances where member_id = 4, but I don't ever want more than once instance where member_id = 4 and group_id = 7. I'm trying to figure out if it's possible to do something like this:

GroupMember.find_or_create(:member_id => 4, :group_id => 7)

我意识到可能有更好的方法来处理这​​个问题，但我喜欢find_or_create的想法的便利。

I realize there may be better ways to handle this, but I like the convenience of the idea of find_or_create.

推荐答案

多个属性可以使用连接的和：

Multiple attributes can be connected with an and:

GroupMember.find_or_create_by_member_id_and_group_id（4,7）

（使用 find_or_initialize_by 如果你不想保存记录的时候了）

(use find_or_initialize_by if you don't want to save the record right away)

编辑：上面的方法去precated在导轨4.新的方式做这将是：

The above method is deprecated in Rails 4. The new way to do it will be:

GroupMember.where(:member_id => 4, :group_id => 7).first_or_create

和

GroupMember.where(:member_id => 4, :group_id => 7).first_or_initialize

编辑2：不是所有这些都分解出来刚铁轨的属性具体的人的。

Edit 2: Not all of these were factored out of rails just the attribute specific ones.

<一个href="https://github.com/rails/rails/blob/4-2-stable/guides/source/active_record_querying.md">https://github.com/rails/rails/blob/4-2-stable/guides/source/active_record_querying.md

示例

GroupMember.find_or_create_by_member_id_and_group_id（4,7）

成为

GroupMember.find_or_create_by（member_id：4，GROUP_ID：7）

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