c ++指针 [英] c++ pointers to operators

问题描述

我有一个问题。我想在c ++（或在c ++ 0x）中写一个指针，这将指向一个操作符af类让我们说A或B.
有任何方法吗？

I've got a problem. I want to write a pointer in c++ (or in c++0x), that will points to a operator af class lets say A or B. Is there any method to do it?

当然有一个语法如

int (A::*_p) ();

但它不能解决这个问题。我想要一般的指针，不要指定它的基类 - 只有操作符功能的指针

but it doesn't solve this problem. I want to make general pointer, not specyfing the base class for it - only pointer for "operator function"

谢谢。

#include <thread>
#include <iostream>

using namespace std;

class A
{
public:
    int operator()()
    {
        return 10;
    }
};

class B
{
public:
    int operator()()
    {
        return 11;
    }
};

int main()
{
 A a;
 int (*_p) ();
 _p = a.operator();
 cout << _p();

 B b;
 _p = b.operator();
 cout << _p();
}

推荐答案

做这个。类类型是运算符成员函数类型的一部分。

No, you can't do this. The class type is a part of the type of the operator member function.

A :: operator（）（）与 B :: operator（）（）的类型不同。前者是 int（A :: *）（）类型，而后者是 int（B :: *）（）。这些类型是完全不相关的。

The type of A::operator()() is different from the type of B::operator()(). The former is of type int (A::*)() while the latter is of type int (B::*)(). Those types are entirely unrelated.

你可以得到的最接近的是使用像C ++ 0x多态函数包装函数 function （在C ++ 0x，C ++ TR1和Boost中找到），并使用 bind 将成员函数指针绑定到类实例：

The closest you can get is by using something like the C++0x polymorphic function wrapper function (found in C++0x, C++ TR1, and Boost) and by using bind to bind the member function pointer to a class instance:

std::function<int()> _p;

A a;
_p = std::bind(&A::operator(), a);
std::cout << _p();

B b;
_p = std::bind(&B::operator(), b);
std::cout << _p();

这篇关于c ++指针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！