如何“触摸”仅当满足某些条件时才创建“belongs_to”关联的父模型？

发布于 2024-12-27 14:31:50 字数 455 浏览 1 评论 0原文

我正在使用 Rails 3.1.0，并且仅当满足某些条件时，我才想“触摸”belongs_to 关联的父模型。

例如，此时我有：

belongs_to :article,
  :touch => true

只有当父模型是“公共”时，我才会“触摸”它。也就是说，Article 类有一个名为 access 的属性（@article.access => public 或 < code>private），我想在“触摸”之前检查这个值：如果这个值不是 public，那么“触摸”它！

是否可以在 belongs_to 关联语句中“直接”实现这一点？如果是这样，怎么办？

原文

I am using Rails 3.1.0 and I would like to "touch" a parent model of a belongs_to association only if certain conditions are met.

For example, at this time I have:

belongs_to :article,
  :touch => true

I would "touch" the parent model only if it is "public". That is, the Article class has an attribute named access (@article.access => public or private) and I would like to check this value before "touching": if this value is not public, then "touch" it!

Is it possible to make that "directly" in the belongs_to association statement? If so, how?

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醉酒的小男人 2025-01-03 14:31:50

你可以像你说的那样尝试 lambda 但我不确定它是否会起作用。像这样的事情：

belongs_to :article, :touch => Proc.new{|o| o.article && o.article.public }

根据实现也许你可以尝试返回nil 而不是 false

belongs_to :article, :touch => Proc.new{|o| o.article && o.article.public ? true : nil }

如果这不起作用，请使用保存前回调，如下所示：

class Model < ActiveRecord::Base
  belongs_to :article

  before_save :touch_public_parent

  def touch_public_parent
    article.touch if article && article.public?
  end
end

如果您有任何问题，请告诉我。

更新 #1

来自 add_touch_callbacks 的相关部分：

if touch_attribute == true
  association.touch unless association.nil?
else
  association.touch(touch_attribute) unless association.nil?
end

因此，如果您传递 true，则对 updated_at 属性进行简单的触摸。如果您传递字段名称，则更新该字段，除非您传递nil。如果你传递 nil 则不会更新任何内容。这就是为什么我说也许你可以尝试第二个版本的belongs_to关联。

You can try lambda as you said but I'm not sure if its going to work. Something like this:

belongs_to :article, :touch => Proc.new{|o| o.article && o.article.public }

According to the implementation maybe you can try to return nil instead of false in the proc, when it's not available

belongs_to :article, :touch => Proc.new{|o| o.article && o.article.public ? true : nil }

If this doesn't works use a before save callback like this:

class Model < ActiveRecord::Base
  belongs_to :article

  before_save :touch_public_parent

  def touch_public_parent
    article.touch if article && article.public?
  end
end

Let me know if you have any questions.

Update #1

The relevant part from add_touch_callbacks:

if touch_attribute == true
  association.touch unless association.nil?
else
  association.touch(touch_attribute) unless association.nil?
end

So if you pass true, then does a simple touch on updated_at attribute. If you pass a field name then updates that field unless you pass nil. If you pass nil doesn't updates nothing. That's why I said that maybe you can try the second version of belongs_to association.

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云归处 2025-01-03 14:31:50

我认为您不能将触摸应用到belongs_to 关联中的条件。

有一种方法有点hacky，但可以直接与belongs_to关联一起工作，

这可能不是推荐的方法

class YourModel
  belongs_to :article
  belongs_to :public_article, :class_name=> "Article", 
             :foreign_key => "article_id", 
             :conditions => {:public => true} , :touch => true 
end

I don't think you can apply touch with a condition in a belongs_to association.

There is a way which is a bit hacky but will work directly with a belongs_to association,

This may not be the recommended way

class YourModel
  belongs_to :article
  belongs_to :public_article, :class_name=> "Article", 
             :foreign_key => "article_id", 
             :conditions => {:public => true} , :touch => true 
end

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