单例模式

 1 #include <iostream>
 2 #include <string>
 3 using namespace std;
 4 
 5 class Singleton
 6 {    
 7 private:
 8     int i;
 9     static Singleton *instance;
10     Singleton(int i)
11     {
12         this->i = i;
13     }
14 public:
15     static Singleton *getInstance()
16     {
17         return instance;
18     }
19     void show()
20     { 
21         cout << i << endl;
22     }
23 };
24 
25 Singleton* Singleton::instance = new Singleton(8899); 
26 
27 class A : public Singleton
28 {
29 
30 };
31 
32 int main()
33 {
34     Singleton *s = Singleton::getInstance();
35     Singleton *s2 = A::getInstance();
36     cout << s << endl;
37     cout << s2 << endl;
38     cout << (s == s2) << endl;
39     return 0;
40 }