何时使用静态成员函数？ [英] When to use static member function?

问题描述

可能的重复项：



C ++：静态成员函数

什么时候在C ++中使用静态成员函数？

When is it appropriate to use a static member function in C++? Please give me a real world example.

推荐答案

静态成员函数的良好用途：

Good uses of static member functions:

• 元编程。现实世界的例子是模板std :: char_traits。所有成员函数都是静态的


• 使它成为一个静态成员函数，它可以访问类的私有成员，虽然这里的朋友也可以。


• 因此，受保护的静态成员函数只能由其派生的类和类访问。

请注意，最后一种情况适用于受保护静态成员函数，但不是私人成员函数。在后一种情况下，你只需将它放入类的编译单元，将其隐藏为实现细节。

Note that the last case applies to a protected static member function but not a private one. In the latter case you would just put it into the compilation unit of the class, hiding it away as an implementation detail. For a protected one though you want it to be visible, albeit in a restricted way.

一个典型的例子是欺骗缺乏友谊的继承。

A typical case of that one is "cheating" the lack of inheritance of friendship.

class B
{
   friend class A;
   // lots of private stuff
};

class A
{
protected:
   static void callsSomePrivateMembers( B& b );
};

class AChild : public A
{
   void foo( B& b );
}

void AChild::foo( B& b )
{
      // AChild does not have private access to B as friendship is not inherited
      // but I do have access to protected members of A including the static ones

    callsSomePrivateMembers( b ); // get to call them through a back-door
}

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