在 Ruby 中查找一个类的所有后代 [英] Look up all descendants of a class in Ruby

问题描述

我可以轻松地在 Ruby 中提升类层次结构:

I can easily ascend the class hierarchy in Ruby:

String.ancestors     # [String, Enumerable, Comparable, Object, Kernel]
Enumerable.ancestors # [Enumerable]
Comparable.ancestors # [Comparable]
Object.ancestors     # [Object, Kernel]
Kernel.ancestors     # [Kernel]

有没有办法降低层次结构?我想这样做

Is there any way to descend the hierarchy as well? I'd like to do this

Animal.descendants      # [Dog, Cat, Human, ...]
Dog.descendants         # [Labrador, GreatDane, Airedale, ...]
Enumerable.descendants  # [String, Array, ...]

但似乎没有 descendants 方法.

(出现这个问题是因为我想在 Rails 应用程序中找到从基类派生的所有模型并列出它们；我有一个可以处理任何此类模型的控制器，我希望能够添加新模型而无需修改控制器.)

(This question comes up because I want to find all the models in a Rails application that descend from a base class and list them; I have a controller that can work with any such model and I'd like to be able to add new models without having to modify the controller.)

推荐答案

这是一个例子:

class Parent
  def self.descendants
    ObjectSpace.each_object(Class).select { |klass| klass < self }
  end
end

class Child < Parent
end

class GrandChild < Child
end

puts Parent.descendants
puts Child.descendants

puts Parent.descendants 给你:

puts Parent.descendants gives you:

GrandChild
Child

puts Child.descendants 给你:

puts Child.descendants gives you:

GrandChild

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