如何Rails的ActiveRecord的表是指本身？ [英] How can Rails' Activerecord table refer to itself?

问题描述

大家。我有一个想法，使用ActiveRecord来实现一些奇怪的如下面的例子：

everyone. I have an idea to use Activerecord to implement something strange like the example below:

SystemInfo < ActiveRecord::Base
  belongs_to :SystemInfo

end

我们的想法是，系统A可以包含系统B作为其子。因此，我将生成应用程序的框架为：

The idea is, System A can contain System B as its child. So I will generate application's skeleton as:

 script/generate scaffold SystemInfo parent_id:integer name:string

然后，当我插入系统A，我将使用系统A的ID作为系统B的PARENT_ID（系统A的PARENT_ID就等于'零'，当我使用的命令是这样的：

and then, when I insert System A, I will use System A's ID as System B's parent_id (System A's parent_id will equal to 'nil'. and when I use the command like this:

sysA = SystemInfo.find_by_id(1) # Get System A

我认为这是可能获得系统A，和它的孩子，系统B.类似的：

I think this is possible to get System A, and it's child, System B. Similar to:

sysA.childrens # Get System B and other SystemInfo which has parent_id == 1 (System A's ID)

您可以建议指引我实现这个想法？我认为这是相当普遍的想法，我们应该能够做到这一点。 ;）

Could you suggest guideline for me to implement this idea? I think this is quite common idea and we should possible to do it. ;)

推荐答案

您有正确的想法。

class SystemInfo < ActiveRecord::Base
  belongs_to :parent, :class_name => 'SystemInfo'
  has_many :children, :class_name => 'SystemInfo', :foreign_key => 'parent_id'
end

s = SystemInfo.find(1)
s.children
# => [...]
s.parent
# => <SystemInfo>

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