在ruby中对Fixnum进行子类化 [英] Sub-classing Fixnum in ruby

问题描述

所以我理解你不应该直接将Fixnum，Float或Integer子类化，因为它们没有#new方法。使用DelegateClass似乎工作，但它是最好的方法吗？有谁知道这些类没有#new背后的原因是什么？

So I understand you aren't supposed to to directly subclass Fixnum, Float or Integer, as they don't have a #new method. Using DelegateClass seems to work though, but is it the best way? Anyone know what the reason behind these classes not having #new is?

我需要一个类似Fixnum的类，但有一些额外的方法，我想要能够通过类中的 self 引用其值，例如：

I need a class which behaves like a Fixnum, but has some extra methods, and I'd like to be able to refer to its value through self from within the class, for example:

class Foo < Fixnum
  def initialize value
    super value
  end

  def increment
    self + 1
  end
end

Foo.new(5).increment + 4 # => 10

推荐答案

您可以非常轻松地设置快速转发实施你自己：

You can pretty easily set up a quick forwarding implementation yourself:

class MyNum
  def initialize(number)
    @number = number
  end

  def method_missing(name, *args, &blk)
    ret = @number.send(name, *args, &blk)
    ret.is_a?(Numeric) ? MyNum.new(ret) : ret
  end
end

然后你可以在MyNum上添加你想要的任何方法，但是你需要在这些方法中使用@number，而不是直接调用super。

Then you can add whatever methods you want on MyNum, but you'll need to operate on @number in those methods, rather than being able to call super directly.

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