访问方法指针到受保护的方法？ [英] Access to method pointer to protected method?

问题描述

此代码：

class B {
 protected:
  void Foo(){}
}

class D : public B {
 public:
  void Baz() {
    Foo();
  }
  void Bar() {
    printf("%x\n", &B::Foo);
  }
}

会出现此错误：

t.cpp: In member function 'void D::Bar()':
Line 3: error: 'void B::Foo()' is protected

• 为什么我可以调用受保护的方法，它的地址？


• 有没有办法标记从派生类完全访问的东西，而不是只能从派生类和 li>
  
  • Why can I call a protected method but not take its address?
  • Is there a way to mark something fully accessible from derived classes rather than only accessible from derived classes and in relation to said derived class?

  BTW：这看起来相关，但是我正在寻找一个引用，在规范等中调用（并且希望这将导致如何使事情按照我期望的方式工作）。

  BTW: This looks related but what I'm looking for a reference to where this is called out in the spec or the like (and hopefully that will lead to how to get things to work the way I was expecting).

  推荐答案

  您可以通过写& D :: Foo 而不是<$ c，通过 D $ c>& B :: Foo 。

  You can take the address through D by writing &D::Foo, instead of &B::Foo.

  查看此编译内容： http://www.ideone.com/22bM4

  但这不会编译（您的代码）： http：/ /www.ideone.com/OpxUy

  But this doesn't compile (your code) : http://www.ideone.com/OpxUy

  为什么我可以调用受保护的方法，

  您不能通过写& B :: Foo Foo 是受保护的成员，您不能从 B 外部访问，地址。但是写& D :: Foo 可以，因为 Foo 成为 D

  You cannot take its address by writing &B::Foo because Foo is a protected member, you cannot access it from outside B, not even its address. But writing &D::Foo, you can, because Foo becomes a member of D through inheritance, and you can get its address, no matter whether its private, protected or public.

  & amp; ; B :: Foo 具有与 b.Foo（）和 pB-> Foo（）在以下代码中：

  &B::Foo has same restriction as b.Foo() and pB->Foo() has, in the following code:

  void Bar() {
      B b;
      b.Foo();     //error - cannot access protected member!
      B *pB = this;
      pB->Foo();   //error - cannot access protected member!
    }
  

  请参阅ideone上的错误：http://www.ideone.com/P26JT

  See error at ideone : http://www.ideone.com/P26JT

  这篇关于访问方法指针到受保护的方法？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！