类型兼容性的解决心方法

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#include <iostream>using namespace std;class parent{public:parent(int a){this->va = a;}virtual void print(void){cout << "基类的a" <<this->va<< endl;}private:int va;};class child : public parent{public:child(int a) : parent(100){this->a = a;}virtual void print(void){cout << "派生类的a" <<this->a<< endl;}private:int a;};int main(){child oop(10);parent oop1(20);parent* p = NULL;p = &oop;p = &oop1;parent &pt = oop;p->print();pt.print();system("pause");return 0;}

* 父类指针可以直接指向子类对象

* 父类引用可以直接指向子类对象

上述结论不管是父类指针还是引用指向子类对像，调用的print都是父类的print，这种解决办法是在print的实现前面加上virtual关键字

实例：

#include <iostream>using namespace std;class parent{public:parent(int a){this->va = a;}virtual void print(void){cout << "基类的a" <<this->va<< endl;}private:int va;};class child : public parent{public:child(int a) : parent(100){this->a = a;}virtual void print(void){cout << "派生类的a" <<this->a<< endl;}private:int a;};void test1(parent* p){p->print();}void test2(parent & pt){pt.print();}int main(){child oop(10);parent oop1(20);parent* p = NULL;p = &oop;p = &oop1;parent &pt = oop;p->print();pt.print();test1(&oop);test1(&oop1);test2(oop);test2(oop1);system("pause");return 0;}

这样就可执行到子类的print了，这里的virtual也可以只加载父类的virtual前，这也是一种多态的调用案例

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