是否有与QUOT; first_or_build＆QUOT;方法对has_many关联？ [英] Is there a "first_or_build" method on has_many associations?

问题描述

在轨3.2+，你可以这样做：

In rails 3.2+, you can do this :

SomeModel.some_scope.first_or_initialize

这意味着你也可以这样做：

Which means you can also do :

OtherModel.some_models.first_or_initialize

我觉得这是pretty的有用的，但我想对我的的has_many first_or_build 方法>关联，这会像 first_or_initialize 不过的还添加了一个新的纪录协会评为建立做的时候需要的。

I find this pretty useful, but i'd like to have a first_or_build method on my has_many associations, which would act like first_or_initialize but also add a new record to the association as build does when needed.

澄清更新：是的，我知道 first_or_initialize 和 first_or_create 。事情是， first_or_initialize 初始化记录不添加到该协会的目标为建立确实，和 first_or_create ...好... 创建的记录，这不是目的。

update for clarification : yes, i know about first_or_initializeand first_or_create. Thing is, first_or_initializedoes not add the initialized record to the association's target as build does, and first_or_create... well... creates a record, which is not the intent.

我有一个解决方案，工程，采用联想扩展：

class OtherModel < ActiveRecord::Base

  has_many :some_models do 
    def first_or_build( attributes = {}, options = {}, &block )
      object = first_or_initialize( attributes, options, &block )
      proxy_association.add_to_target( object ) if object.new_record?
      object
    end
  end

end

我只是想知道：

• 内置解决这个问题已经存在？
• 在我的实现有缺陷，我不明白吗？

推荐答案

我不知道是否有任何内置的轨道，将做你想要什么，但你可以有更多的模仿first_or_initialize code简洁的扩展名不是你目前正在使用，我相信你想要做什么，并把它包装成一个可重用的扩展名，例如下面。这是写与Rails 3.2扩展格式。

I'm not sure if there is anything built into rails that will do exactly what you want, but you could mimic the first_or_initialize code with a more concise extension than you are currently using, which I believe does what you want, and wrap it into a reusable extension such as the following. This is written with the Rails 3.2 extend format.

module FirstOrBuild
  def first_or_build(attributes = nil, options = {}, &block)
    first || build(attributes, options, &block)
  end
end

class OtherModel < ActiveRecord::Base
  has_many :some_models, :extend => FirstOrBuild
end

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