类模板/函数模板实现父类指针指向子类对象(虚函数实现多态)

// main.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
//#include <windows.h>
#include <iostream>
using namespace std;


template<class T>
class SingletonInstance
{
public:
    static T* GetInstance()
    {
        if (nullptr == _pInstance)
        {
            _pInstance = new T();
            printf("instance successful!
");
        }
        return _pInstance;
    }

private:
    SingletonInstance() :_pInstance(nullptr) {}
    ~SingletonInstance()
    {
        if (nullptr != _pInstance)
        {
            delete _pInstance;
            _pInstance = nullptr;
        }
    }

private:
    static T* _pInstance;
};

template<class T>
T* SingletonInstance<T>::_pInstance = NULL;



template<class func>
func* exchange(func param)
{
    return &param;
}


class Temp
{
public:
    Temp()
    {
        /*printf("hello temp
");*/
    }
    virtual int linkfunction(void)
    {
        printf("hello temp
");
        return -1;
    }
};


class sonTemp: public Temp
{
public:
    int linkfunction(void) override
    {
        printf("hello son temp
");
        return 0;
    }
};


int main(int argc, _TCHAR* argv[])
{
    // 类模板
    Temp *aa = SingletonInstance<sonTemp>::GetInstance();
    int bb = aa->linkfunction();
    printf("bb = %d
", bb);



    // 函数模板
    sonTemp *obj = new sonTemp();
    Temp *func = exchange(*obj);
    int ret = func->linkfunction();
    printf("ret = %d
", ret);

    return 0;
}