c++重载操作符研究之 operator ->()

来源：互联网发布：java将object转为date 编辑：程序博客网时间：2024/05/19 06:39

本章是介绍重载操作符 -> 的研究，上代码先

#include "stdafx.h"#include <iostream>#include <string>template<typename T>class A1 {public:    A1(T* t) : m_imp(t) {        std::cout << "A1()" << std::endl;    }    ~A1() {        std::cout << __FUNCTION__ << std::endl;    }    T* operator ->() {        std::cout << __FUNCTION__ << std::endl;        return m_imp;    }private:    T* m_imp;};template<typename T>class A2 {public:    A2(T* t) : m_imp(t) {}    A1<T> operator ->() {        std::cout << __FUNCTION__ << std::endl;        A1<T> a(m_imp);        return a;    }private:    T* m_imp;};template<typename T>class A3 {public:    A3(T* t) : m_imp(t) {}    A2<T> operator ->() {        std::cout << __FUNCTION__ << std::endl;        A2<T> a(m_imp);        return a;    }private:    T* m_imp;};class Test {public:    void show() {        std::cout << m_a << std::endl;    }private:    int m_a;};template<typename T>class B1 {public:    B1(T* t) : m_imp(t) {        std::cout << __FUNCTION__ << std::endl;    }    B1(T& t) : m_imp(&t) {        std::cout << __FUNCTION__ << std::endl;    }    T* operator->() {        std::cout << __FUNCTION__ << std::endl;        return m_imp;    }private:    T* m_imp;};int _tmain(int argc, _TCHAR* argv[]){    Test* pt = new Test();    A1<Test> a1(pt);    a1->show();    a1.A1::operator ->()->show();    A2<Test> a2(pt);    a2->show();    // 可自动推导出如下式    // a2.A2::operator ->().A1::operator ->()->show();    A3<Test> a3(pt);    a3->show();    // 可自动推导出如下式    // a3.A3<Test>::operator ->().A2::operator ->().A1::operator ->()->show();    B1<Test> b1(pt);    b1->show();    B1<B1<Test> > b2(b1);    b2->operator ->()->show();    b2.B1<B1<Test> >::operator ->()->B1<Test>::operator ->()->show();    // b2->show(); 错误，不能递归推导return 0;}

基于以上代码，可以看出对->运算符的重载,编译器无法进行递归推导.

这种递归推导，编译器可以在编译期处理，为什么编译器不处理这种递归推导，留待思考

以上代码在vc编译器测试通过。