C++的Singleton模式实现

    Singleton.h

    class A {
    private:
        static A *_instance;
    protected:
        A();
    public:
        static A* getInstance();
        void sayhello();
    };

    Singleton.cpp

    #include <iostream>
    #include "singleton.h"
    using namespace std;

    A* A::_instance = 0;

    A::A() {}
    A* A::getInstance() {
        if (_instance == 0)
            _instance = new A;
        return _instance;
    }
    void A::sayhello() {
        cout << "Hello!" << endl;
    }

    testsingleton.cpp

    #include "singleton.h"
    #include <iostream>
    using namespace std;

    int main()
    {
        A *abc = A::getInstance();
        abc->sayhello();
        return 0;
    }