C++类静态对象的问题

[阿尔博特]

#include <iostream>
using namespace std;

class Base
{
public:
    Base()
    {   
        m_p = this;
    }   
    virtual void func() { m_p->print(); }

    virtual void print() { cout << "Base" << endl; }

    static Base* m_p;
};

Base * Base::m_p = NULL;

class Derive : public Base
{
public:
    void print() { cout << "Derive" << endl; }
};

int main()
{
    Base * pDerive = new Derive;
    Base * pBase = new Base;
    pBase->func();
    pDerive->func();
    return 0;
}

打印
Base
Base
如果
int main()
{
Base * pBase = new Base;
Base * pDerive = new Derive;
pBase->func();
pDerive->func();
return 0;
}
这样写打印
Derive
Derive
为什么会结果不一样

[幻夢之葉]

class Derive : public Base { public: //少了virtual关键字 virtual void print() { cout << "Derive" << endl; } };

[Van_Le]

引用 楼主 jackhanzy 的回复:

#include <iostream>
using namespace std;

class Base
{
public:
    Base()
    {   
        m_p = this;
    }   
    virtual void func() { m_p->print(); }

    virtual void print() { cout << "Base" << endl; }

    static Base* m_p;
};

Base * Base::m_p = NULL;

class Derive : public Base
{
public:
    void print() { cout << "Derive" << endl; }
};

int main()
{
    Base * pDerive = new Derive;
    Base * pBase = new Base;
    pBase->func();
    pDerive->func();
    return 0;
}

打印 Base Base 如果 int main() { Base * pBase = new Base; Base * pDerive = new Derive; pBase->func(); pDerive->func(); return 0; } 这样写打印 Derive Derive 为什么会结果不一样

m_p是静态变量，所有的类中只含有一个该对象，每次创建新的对象时m_p=this都要执行一遍，所以最后的结果取决于，最后一次是哪个类。换句话说，最后一次创建的类，决定m_p的类型。

[我看你有戏]

Base * pBase = new Base; Base * pDerive = new Derive; 这两句先后顺序变一下，那就打印base了