c++ 多态

示例代码对以下两种情况进行了说明：

1. 继承时改变虚函数的权限；

2. 私有继承；

class A 
{
public:
    virtual void test1() {
        cout << "public test1 of A" << endl;
    }
private:
    virtual void test2() {
        cout << "private test2 of A" << endl;
    }
protected:
    int p1;
private:
    int p2;
};

class B: public A
{
private:
    void test1() {
        cout << "privte test1 of B" << endl;
    }
public:
    void test2() {
        cout << "public test2 of B" << endl;
    }

};

class C: private A
{
public:
    void testProtected() {
        cout << p1 << endl;
    }
};

class D: public C
{
public:
    void testProtected() {
        // cout << p1 << endl;//因为c私有继承A，c不能访问a的protedted成员
    }
};

int main()  {
    B b;
    A* a = &b;

    a->test1();//可以访问， 权限以A为准
    // a->test2();//无法访问私有成员

    C c;
　　 c.testProtected();　
    return 0;

}