通过与现有的对象关联的has_many / ActiveRecord的 [英] has_many through association with existing object / ActiveRecord

问题描述

由于模型

class Composition < ActiveRecord::Base
  attr_accessible :content

  has_many :compositions_tags
  has_many :tags, :through => :compositions_tags

end

class Tag < ActiveRecord::Base
  attr_accessible :text

  has_many :compositions_tags
  has_many :compositions, :through => :compositions_tags

  validates_uniqueness_of :tag, only: [:create, :update], message: "already taken"
end

class CompositionsTag < ActiveRecord::Base
  belongs_to :composition
  belongs_to :tag
end

现在，比如我做的

Composition.create(content: "Hello").tags.create(text: "#hi")

其结果将是一个成分与内容的Hello，并与文字一个变量#hi具有创建

The result would be is a Composition with content "Hello" and a Tag with text "#hi" having created.

然后，我再创建一个成分。

Then I create again a Composition.

Composition.create(content: "Goodmorning")

现在是什么我不知道，想要做的就是联想的以及现有的标记文本#hi。

Now what I don't know and wanted to do is associate that as well to the existing Tag with text "#hi".

我要如何做，在最优雅的方式？

How do I do that in the most elegant way?

推荐答案

如果您是灵活的，你创建的记录的顺序，您可以创建标签，然后在同一行创建两个组成：

If you are flexible on the order in which you create your records, you can create the tag and then create the two compositions in one line:

Tag.create(text: "#hi").compositions.create([{content: "Goodmorning"},{content: "Hello"}])

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