Ruby-on-rails Rails - 如何使用查找或创建

Rails - How to use Find Or Create

提问by AnApprentice

I have the following:

我有以下几点：

@permission = @group.permissions.create(
  :user_id => @user.id,
  :role_id => 2,
  :creator_id => current_user.id)

How can I update that to be find_or_create, so that if this record already exists, it's assigned to @permission, and if it doesn't exist, the record is created?

如何将其更新为find_or_create，以便如果此记录已存在，则将其分配给@permission，如果不存在，则创建该记录？

回答by Gavin Miller

While the accepted answer is correctit's important to note that in Rails 4 this syntax will be changing (and the hash syntax). You should be writing the following:

虽然接受的答案是正确的，但重要的是要注意，在 Rails 4 中，此语法将发生变化（以及哈希语法）。您应该编写以下内容：

@permission = Permission.where(
  user_id: @user.id, 
  role_id: 2, 
  creator_id: current_user.id).first_or_create

Which actually looks much closer to your original method! See the sub-section Deprecated Findersfor more details.

这实际上看起来更接近您的原始方法！有关更多详细信息，请参阅已弃用的 Finders小节。

回答by fl00r

Related topic:

相关主题：

find_or_create_by in Rails 3 and updating for creating records

Rails 3 中的 find_or_create_by 和更新以创建记录

You can extend ActiveRecord with your own update_or_createmethod (see related topic) and then you can use this

您可以使用自己的update_or_create方法扩展 ActiveRecord （请参阅相关主题），然后您可以使用它

@permission = Permission.update_or_create_by_user_id_and_role_id_and_creator_id(@user.id, 2, current_user.id) do |p|
  p.group_id = @group.id
end

Or you can use find_or_create_by...method:

或者你可以使用find_or_create_by...方法：

@permission = Permission.find_or_create_by_user_id_and_role_id_and_creator_id(@user.id, 2, current_user.id)
@permission.group = @group
@permission.save

回答by Blair Anderson

I'm updating questions with versioned answers. Because its important.

我正在用版本化的答案更新问题。因为它很重要。

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Rails 4 (docs)

Rails 4（文档）

There are a few ways to "find or create" an object, one is find_or_create_by(args)

有几种方法可以“查找或创建”一个对象，一种是 find_or_create_by(args)

Client.find_or_create_by(email: "[email protected]", phone: "4255551212")

But the community preferredwayis using where

但社区首选的方式是使用where

client = Client.where(email: "[email protected]", phone: "4255551212").first_or_create

client = Client.where(email: "[email protected]", phone: "4255551212").first_or_create

and then you can do something like:

然后你可以做这样的事情：

client = Client.where(client_params.slice(:email, :phone)).first_or_create
client.update(client_params)

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Rails 3 (docs)

Rails 3（文档）

Suppose you want to find a client named ‘Andy', and if there's none, create one and additionally set his locked attribute to false. You can do so by running:

假设您要查找名为“Andy”的客户端，如果没有，则创建一个并将其锁定属性设置为 false。您可以通过运行：

client = Client.where(:first_name => 'Andy').first_or_create(:locked => false)
# => #<Client id: 1, first_name: "Andy", orders_count: 0, locked: false, created_at: "2011-08-30 06:09:27", updated_at: "2011-08-30 06:09:27">

回答by lkahtz

Or you wanna try this if you have many fields to fill in:

或者，如果您有很多字段要填写，您想试试这个：

conditions = { :user_id => @user.id, 
               :role_id => 2,
               :creator_id => current_user.id }

    @permission = group.permissions.find(:first, :conditions => conditions) || group.permissions.create(conditions)

see this post: How can I pass multiple attributes to find_or_create_by in Rails 3?

请参阅这篇文章： 如何在 Rails 3 中将多个属性传递给 find_or_create_by？