Vehicle 一个车辆的虚基类

class Vehicle {

public:

virtual double weight()const = 0;

virtual void start() = 0;

virtual Vehicle* copy() = 0;

virtual ~Vehicle() {};

};

 

衍生出RoadVehicle AutoVehicle两个类

如果有一个停车场类 可以容纳100辆车

一开始计划 有Vehicle[100]这种变量来表示停车场

但是Vehicle是虚基类 不能有实例化的实体 也就不会有数组

所以需要一个代理类来保存Vehicle的指针 它可以指向任意的Vehicle的衍生类

同时考虑到拷贝操作 添加了拷贝函数

class VehicelSurrogate {

public:

VehicelSurrogate() :vp(0) {};

VehicelSurrogate( Vehicle& v) :vp(v.copy()) {};

VehicelSurrogate(const VehicelSurrogate& v):vp(v.vp ? v.vp->copy() : 0) {};

~VehicelSurrogate() {

delete vp;

};

VehicelSurrogate& operator=(const VehicelSurrogate& v) {

if (this != &v) {

delete vp;

vp = (v.vp ? v.vp->copy() : 0);

}

return *this;

};

double weight() {

return vp->weight();

}

private:

Vehicle* vp;

};

 

如此 就可以使用VehicelSurrogate[100]来表示停车场的概念

完整代码如下

1 // test5.cpp: 定义控制台应用程序的入口点。 2 // 3  4 #include "stdafx.h" 5 #include 
      
        6  7 class Vehicle { 8 public: 9     virtual double weight()const = 0;10     virtual void start() = 0;11     virtual Vehicle* copy() = 0;12     virtual ~Vehicle() {};13 };14 15 class RoadVehicle:public Vehicle{16 public:17     virtual double weight() const{18         return 1;19     }20     virtual void start() {}21     virtual Vehicle* copy() {22         return new RoadVehicle(*this);23     }24     virtual ~RoadVehicle() {}25 };26 class AutoVehicle:public RoadVehicle{27 public:28     virtual double weight() const{29         return 2;30     }31     virtual void start() {}32     virtual Vehicle* copy() {33         return new AutoVehicle(*this);34     }35     virtual ~AutoVehicle() {}36 37 };38 39 40 class VehicelSurrogate {41 public:42     VehicelSurrogate() :vp(0) {};43     VehicelSurrogate( Vehicle& v) :vp(v.copy()) {};44     VehicelSurrogate(const VehicelSurrogate& v):vp(v.vp ? v.vp->copy() : 0) {};45     ~VehicelSurrogate() {46         delete vp;47     };48     VehicelSurrogate& operator=(const VehicelSurrogate& v) {49         if (this != &v) {50             delete vp;51             vp = (v.vp ? v.vp->copy() : 0);52         }53         return *this;54     };55     double weight() {56         return vp->weight();57     }58 59 private:60     Vehicle* vp;61 };62 63 64 int main()65 {66     VehicelSurrogate parking_lot[100];67     AutoVehicle x;68     parking_lot[0] = x;69     std::cout << parking_lot[0].weight() << std::endl;;70     return 0;71 }