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如何使基类方法在ruby中不可重写?

override oop ruby

2

Chirantan · 技术社区 · 16 年前

class A
  def dont_override_me
    puts 'class A saying, "Thank you for not overriding me!"'
  end
end

以及另一个扩展A并试图重写 dont_override_me 方法。

class B < A
  def dont_override_me
    puts 'class B saying, "This is my implementation!"'        
  end
end

如果我实例化B并调用 ,将调用类B的实例方法。

b = B.new
b.dont_override_me # => class B saying, "This is my implementation!"

这是因为ruby的特性。可以理解。

不要凌驾于我之上 final 在java for ruby中。在C++中,基类方法可以非虚拟化,以便它们由派生类变得不可重写。我如何在ruby中实现这一点?

4 回复 | 直到 16 年前

1

6

Steven Robbins 16 年前

你可以通过挂起更改事件并将其更改回来来完成,但对我来说,这似乎有点臭:

http://scie.nti.st/2008/9/17/making-methods-immutable-in-ruby

2

4

Gdeglin 16 年前

有一种方法: http://www.thesorensens.org/2006/10/06/final-methods-in-ruby-prevent-method-override/

它还被打包到一个名为“finalizer”(gem install finalizer)的gem中

这将使用添加了方法的回调,并将新方法名与要生成的方法列表进行比较 final

3

1

Mario Narcis Radoi 15 年前

class A #This is just as you've already defined it.
  def dont_override_me
    puts 'class A saying, "Thank you for not overriding me!"'
  end
end

module BehaviorForB
  def dont_override_me
    puts 'class B saying, "This is my implementation!"'        
  end

  def greet
    "Hello, Friend."
  end
end

class B < A
  include BehaviorForB
end

b = B.new
b.dont_override_me #=> class A saying, "Thank you for not overriding me!"
b.greet #=> Hello, Friend.

4

0

MVP 8 年前

一种防止方法被子类重写的方法(但不建议这样做):

class Class
  def frozen_method(method)
    if class_variable_defined?(:@@__frozen_methods__)
      add= class_variable_get(:@@__frozen_methods__) | [method]
      class_variable_set(:@@__frozen_methods__,add)
    else
      class_variable_set(:@@__frozen_methods__,[method])
    end
    class << self
      def inherited(child)
        def method_added(method)
          if class_variable_get(:@@__frozen_methods__).include? method
            send(:remove_method, method)
            error="Cannot change method #{method} because it's not overridde"
            raise TypeError, error
          end
        end
      end
    end
  end
end

class Foo
  def hello
    'hello'
  end
  def foo
    'foo'
  end

  frozen_method :foo
end

class Bar < Foo
  def foo
    'new foo'
  end
end

#=> TypeError: Cannot change method foo because it's not overridde

Bar.new.foo  #=> 'foo'

警告:此示例不完整。如果你加上 frozen_method