c++设计模式之单例模式下的实例自动销毁(垃圾自动回收器)

 1 #include <iostream>
 2 using namespace std;
 3 
 4 class Singleton
 5 {
 6 public:
 7     static Singleton *GetInstance()
 8     {
 9         if (m_Instance == NULL)
10         {
11             m_Instance = new Singleton();
12             cout<<"get Singleton instance success"<<endl;
13         }
14         return m_Instance;
15     }
16 
17 private:
18     Singleton(){cout<<"Singleton construction"<<endl;}
19     static Singleton *m_Instance;
20 
21     // This is important
22     class GC // 垃圾回收类
23     {
24     public:
25         GC()
26         {
27             cout<<"GC construction"<<endl;
28         }
29         ~GC()
30         {
31             cout<<"GC destruction"<<endl;
32             // We can destory all the resouce here, eg:db connector, file handle and so on
33             if (m_Instance != NULL)
34             {
35                 delete m_Instance;
36                 m_Instance = NULL;
37                 cout<<"Singleton destruction"<<endl;
38                 system("pause");//不暂停程序会自动退出，看不清输出信息
39             }
40         }
41     };
42     static GC gc;  //垃圾回收类的静态成员
43 
44 };
45 
46 Singleton *Singleton::m_Instance = NULL;
47 Singleton::GC Singleton::gc; //类的静态成员需要类外部初始化，这一点很重要，否则程序运行连GC的构造都不会进入，何谈自动析构
48 int main(int argc, char *argv[])
49 {
50     Singleton *singletonObj = Singleton::GetInstance();
51     return 0;
52 }