如何实施"公共/受保护/私有"方法,以及如何模拟它？

Question

在ruby中,你可以这样做:

class Thing
  public
  def f1
    puts "f1"
  end

  private
  def f2
    puts "f2"
  end

  public
  def f3
    puts "f3"
  end

  private
  def f4
    puts "f4"
  end
end

现在f1和f3以及public,f2和f4是私有的.内部发生了什么,允许您调用一个类方法然后更改方法定义？我怎样才能实现相同的功能(表面上是为了创建我自己的java注释)

例如...

class Thing
  fun
  def f1
    puts "hey"
  end

  notfun
  def f2
    puts "hey"
  end
end

而fun和notfun将改变以下函数定义.

谢谢

Answer 1

你有时可以将红宝石推入espressso杯中.我们来看看如何.

这是FunNotFun模块......

module FunNotFun

  def fun
    @method_type = 'fun'
  end

  def notfun
    @method_type = 'not fun'
  end

  def method_added(id)
    return unless @method_type
    return if @bypass_method_added_hook
    orig_method = instance_method(id)
    @bypass_method_added_hook = true
    method_type = @method_type
    define_method(id) do |*args|
      orig_method.bind(self).call(*args).tap do
        puts "That was #{method_type}"
      end
    end
    @bypass_method_added_hook = false
  end

end

...你可以用来扩展一个班级......

class Thing

  extend FunNotFun

  fun
  def f1
    puts "hey"
  end

  notfun
  def f2
    puts "hey"
  end
end

......结果如下:

Thing.new.f1
# => hey
# => That was fun

Thing.new.f2
# => hey
# => That was not fun

但是请参阅下面的行以获得更好的方法.

注释(参见normalocity的答案)不那么麻烦,作为一种常见的Ruby习语,将更容易传达代码的意图.以下是如何使用注释执行此操作:

module FunNotFun

  def fun(method_id)
    wrap_method(method_id, "fun")
  end

  def notfun(method_id)
    wrap_method(method_id, "not fun")
  end

  def wrap_method(method_id, type_of_method)
    orig_method = instance_method(method_id)
    define_method(method_id) do |*args|
      orig_method.bind(self).call(*args).tap do
        puts "That was #{type_of_method}"
      end
    end
  end

end

在使用中,注释是在定义方法之后而不是之前:

class Thing

  extend FunNotFun

  def f1
    puts "hey"
  end
  fun :f1

  def f2
    puts "hey"
  end
  notfun :f2

end

结果是一样的:

Thing.new.f1
# => hey
# => That was fun

Thing.new.f2
# => hey
# => That was not fun