<span style="font-size:16px;">#include <iostream>#include<string> using namespace std; class Animal { public: virtual void cry() const = 0; //声明纯虚函数,供派生类定义使用protected: string name; }; class Mouse: public Animal { public: Mouse(string name){this->name = name;} virtual void cry() const {cout << "我叫" << name << ",是一只老鼠,我的叫声是:吱吱吱!" << endl;} }; class Cat: public Animal { public: Cat(string name){this->name = name;} virtual void cry() const {cout << "我叫" << name << ",是一只猫,我的叫声是:喵喵喵!" << endl;} }; class Dog: public Animal { public: Dog(string name){this->name = name;} virtual void cry() const {cout << "我叫" << name << ",是一条狗,我的叫声是:汪汪汪!" << endl;} }; class Giraffe: public Animal { public: Giraffe(string name){this->name = name;} virtual void cry() const {cout << "我叫" << name << ", 是长颈鹿,脖子太长,发不出声音来!" << endl;} }; int main( ) { Animal *p; //p = new Animal(); p->cry(); //输出: 不知哪种动物,让我如何学叫?(问题出自此处) Mouse m("Jerry"); p = &m; p->cry(); //输出: 我叫Jerry,是一只老鼠,我的叫声是:吱吱吱! Cat c("Tom"); p = &c; p->cry(); //输出: 我叫Tom,是一只猫,我的叫声是:喵喵喵! Dog d("Droopy"); p = &d; p->cry(); //输出: 我叫Droopy,是一条狗,我的叫声是:汪汪汪! Giraffe g("Gill"); p = &g; p->cry(); //输出: 我叫Gill,是长颈鹿,脖子太长,发不出声音来! system("pause"); return 0; } </span>![](http://my.csdn.net/uploads/201205/21/1337570682_2957.jpg)