如何一个 - 没有继承 - 重写一个类方法，并从新的方法中调用原始？ [英] How does one - without inheritance - override a class method and call the original from within the new method?

问题描述

我找到一个成功替代 Time.strftime 的来源，如下所示：

I found one source which successfully overrode Time.strftime like this:

class Time
  alias :old_strftime :strftime
  def strftime
    #do something
    old_strftime
  end
end

麻烦的是， strftime 是一个实例方法。我需要重写 Time.now - 一个类方法 - 在任何调用者获取我的新方法，而新方法仍然调用原来的 .now 方法。我看过 alias_method ，并且没有成功。

The trouble is, strftime is an instance method. I need to override Time.now - a class method - in such away that any caller gets my new method, while the new method still calls the original .now method. I've looked at alias_method and have met with no success.

推荐答案

这有时很难得到你的头，但是你需要打开eigenclass这是与特定类对象相关联的单例。该语法是类<<自我...结束。

This is kinda hard to get your head around sometimes, but you need to open the "eigenclass" which is the singleton associated with a specific class object. the syntax for this is class << self do...end.

class Time
  alias :old_strftime :strftime

  def strftime
    puts "got here"
    old_strftime
  end
end

class Time
  class << self
    alias :old_now :now
    def now
      puts "got here too"
      old_now
    end
  end
end

t = Time.now
puts t.strftime

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