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多态的用途
发布时间：2025/4/5
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通过上面的例子读者可能还未发现多态的用途，不过确实也是，多态在小项目中鲜有有用武之地。
接下来的例子中，我们假设你正在玩一款军事游戏，敌人突然发动了地面战争，于是你命令陆军、空军及其所有现役装备进入作战状态。具体的代码如下所示：
#include <iostream> using namespace std; //军队 class Troops{ public:virtual void fight(){ cout<<"Strike back!"<<endl; } }; //陆军 class Army: public Troops{ public:void fight(){ cout<<"--Army is fighting!"<<endl; } }; //99A主战坦克 class _99A: public Army{ public:void fight(){ cout<<"----99A(Tank) is fighting!"<<endl; } }; //武直10武装直升机 class WZ_10: public Army{ public:void fight(){ cout<<"----WZ-10(Helicopter) is fighting!"<<endl; } }; //长剑10巡航导弹 class CJ_10: public Army{ public:void fight(){ cout<<"----CJ-10(Missile) is fighting!"<<endl; } }; //空军 class AirForce: public Troops{ public:void fight(){ cout<<"--AirForce is fighting!"<<endl; } }; //J-20隐形歼击机 class J_20: public AirForce{ public:void fight(){ cout<<"----J-20(Fighter Plane) is fighting!"<<endl; } }; //CH5无人机 class CH_5: public AirForce{ public:void fight(){ cout<<"----CH-5(UAV) is fighting!"<<endl; } }; //轰6K轰炸机 class H_6K: public AirForce{ public:void fight(){ cout<<"----H-6K(Bomber) is fighting!"<<endl; } }; int main(){Troops *p = new Troops;p ->fight();//陆军p = new Army;p ->fight();p = new _99A;p -> fight();p = new WZ_10;p -> fight();p = new CJ_10;p -> fight();//空军p = new AirForce;p -> fight();p = new J_20;p -> fight();p = new CH_5;p -> fight();p = new H_6K;p -> fight();return 0; } Strike back! --Army is fighting! ----99A(Tank) is fighting! ----WZ-10(Helicopter) is fighting! ----CJ-10(Missile) is fighting! --AirForce is fighting! ----J-20(Fighter Plane) is fighting! ----CH-5(UAV) is fighting! ----H-6K(Bomber) is fighting!这个例子中的派生类比较多，如果不使用多态，那么就需要定义多个指针变量，很容易造成混乱；而有了多态，只需要一个指针变量 p 就可以调用所有派生类的虚函数。
从这个例子中也可以发现，对于具有复杂继承关系的大中型程序，多态可以增加其灵活性，让代码更具有表现力。
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