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)

 1 // main.cpp : Defines the entry point for the console application.
 2 //
 3 
 4 #include "stdafx.h"
 5 //#include <windows.h>
 6 #include <iostream>
 7 using namespace std;
 8 
 9 
10 template<class T>
11 class SingletonInstance
12 {
13 public:
14     static T* GetInstance()
15     {
16         if (nullptr == _pInstance)
17         {
18             _pInstance = new T();
19             printf("instance successful!
");
20         }
21         return _pInstance;
22     }
23 
24 private:
25     SingletonInstance() :_pInstance(nullptr) {}
26     ~SingletonInstance()
27     {
28         if (nullptr != _pInstance)
29         {
30             delete _pInstance;
31             _pInstance = nullptr;
32         }
33     }
34 
35 private:
36     static T* _pInstance;
37 };
38 
39 template<class T>
40 T* SingletonInstance<T>::_pInstance = NULL;
41 
42 
43 
44 template<class func>
45 func* exchange(func param)
46 {
47     return &param;
48 }
49 
50 
51 class Temp
52 {
53 public:
54     Temp()
55     {
56         /*printf("hello temp
");*/
57     }
58     virtual int linkfunction(void)
59     {
60         printf("hello temp
");
61         return -1;
62     }
63 };
64 
65 
66 class sonTemp: public Temp
67 {
68 public:
69     int linkfunction(void) override
70     {
71         printf("hello son temp
");
72         return 0;
73     }
74 };
75 
76 
77 int main(int argc, _TCHAR* argv[])
78 {
79     // 类模板
80     Temp *aa = SingletonInstance<sonTemp>::GetInstance();
81     int bb = aa->linkfunction();
82     printf("bb = %d
", bb);
83 
84 
85 
86     // 函数模板
87     sonTemp *obj = new sonTemp();
88     Temp *func = exchange(*obj);
89     int ret = func->linkfunction();
90     printf("ret = %d
", ret);
91 
92     return 0;
93 }