使用 has_many 重新创建此自定义查询

发布于 2024-07-26 06:55:47 字数 565 浏览 4 评论 0原文

我希望这将是一个简单的:)我已经花了几个小时玩 has_many 选项试图模拟这一点：

has_many :pages, :finder_sql => %q(SELECT * FROM `pages` LEFT OUTER JOIN `component_instances` ON `component_instances`.instance_id = `pages`.id AND `component_instances`.instance_type = 'Page' WHERE `component_instances`.parent_id = #{id})

它基本上是一个多态连接，所以有一个 component_instances 表充当中心结构并具有不同的功能挂在上面的东西类型。这是一个嵌套集（在本例中这并不重要）。

问题似乎是 has_many 不允许我操纵连接条件。而且我无法取消自动创建的外键连接条件。

上面的代码有效，但我想在结果上使用范围，而这对于自定义查询是不可能的。

任何帮助将不胜感激:)

干杯，

布伦登

原文

I'm hoping this will be an easy one :) I've been stuffing around for hours playing with the has_many options trying to emulate this:

has_many :pages, :finder_sql => %q(SELECT * FROM `pages` LEFT OUTER JOIN `component_instances` ON `component_instances`.instance_id = `pages`.id AND `component_instances`.instance_type = 'Page' WHERE `component_instances`.parent_id = #{id})

It's basically a polymorphic join so there is the component_instances table that acts as a central structure and has different types of things hanging off of it. It's a nested set (not that that matters in this case).

The problem seems to be that has_many doesn't allow me to manipulate the join conditions. And I can't nullify the foreign key join condition that's automatically made.

The above code works but I want to use scopes on the results, and that's not possible with a custom query.

Any help would be greatly appreciated :)

Cheers,

Brendon

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永不分离 2024-08-02 06:55:47

您可以使用 :through 选项来执行此操作。

has_many :pages, :through => :component_instances, :source => :parent, :source_type => 'Page'

You can do this with the :through option.

has_many :pages, :through => :component_instances, :source => :parent, :source_type => 'Page'

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栀梦 2024-08-02 06:55:47

感谢迈克尔的领导，最终这成功了：

  has_one :page_set, :foreign_key => :parent_id
  belongs_to :instance, :polymorphic => true, :dependent => :destroy
  has_many :pages, :through => :page_set, :source => :instance, :source_type => 'Page', :extend => LearningCaveFilterExtension

但它有点粗略，因为 :page_set 方法实际上返回了完全错误的东西。理想情况下它应该返回 self，但我需要将 :parent_id 作为外键，以便从 has_many 页面声明生成的 SQL 是正确的（使用 :id 是正确的方法，但随后会搞砸 :pages 方法。:) 我的头脑还没有完全弄清楚这里发生了什么，但至少它有效并且范围界定也有效:)

感谢您的帮助，如果您对为什么有效有任何解释，请告诉我:)

Thanks for the lead Michael, in the end this worked:

  has_one :page_set, :foreign_key => :parent_id
  belongs_to :instance, :polymorphic => true, :dependent => :destroy
  has_many :pages, :through => :page_set, :source => :instance, :source_type => 'Page', :extend => LearningCaveFilterExtension

but it's a little bit sketchy as the :page_set method actually returns something completely wrong. Ideally it should return self but I needed to put :parent_id as the foreign key so that the SQL generated from the has_many pages declaration was correct (using :id would be the correct way but then that screws up the :pages method. :) My mind hasn't quite gotten around what's going on here, but at least it works and scoping works too :)

Thanks for the help, and if you have any explanations as to why that works, please let me know :)

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诗化ㄋ丶相逢 2024-08-02 06:55:47

哈哈，睡在上面给了我答案：

class PageSet < ActiveRecord::Base

  unloadable

  set_table_name "component_instances"

  has_many :children, :foreign_key => :parent_id, :class_name => 'PageSet'
  belongs_to :instance, :polymorphic => true, :dependent => :destroy
  has_many :pages, :through => :children, :source => :instance, :source_type => 'Page'

end

通过 Parent_id 链接的实体是正确的子实体，我只是以错误的方式引用它们，但 AR 没有引发任何错误:)

Lol, sleeping on it gave me the answer:

class PageSet < ActiveRecord::Base

  unloadable

  set_table_name "component_instances"

  has_many :children, :foreign_key => :parent_id, :class_name => 'PageSet'
  belongs_to :instance, :polymorphic => true, :dependent => :destroy
  has_many :pages, :through => :children, :source => :instance, :source_type => 'Page'

end

The entities with the link through parent_id are rightly children, I was just referring to them in the wrong way, but AR didn't raise any errors :)

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