多态性典型案例.doc

第八章 多态性典型案例【案例8-1】编写矩形类重载成员函数#include#include#includeusing namespace std;class CRectlong left; long top;long right; long bottom;public: CRect(int l=1, int t=2, int r=3, int b=4);void SetRect(int x1, int y1, int x2, int y2); /重载的成员函数void SetRect(const CRect& r) ; /重载的成员函数 void Disp();void CRect:Disp() /成员函数显示自身的数据coutleft=left; top=top; right=right; bottom=right = right;this-bottom = bottom;int main()CRect r,s; /调用构造函数CRect(1, 2, 3, 4)定义对象r.Disp(); /r对象显示数据r.SetRect(5,6,7,8); s.SetRect(r); /调用重载的成员函数 s.Disp(); /显示s对象数据return 0; 【案例8-2】电话号码类PhoneNumber重载流提取与流插入运算符#include #include using namespace std;class PhoneNumber /重载流插入操作符，如果需要使用cout somePhoneNumber;则不能重载为成员函数friend ostream &operator( ostream &output, const PhoneNumber &num ) output ( num.areaCode ) num.exchange - somePhoneNumber;则不能重载为成员函数friend istream &operator( istream &input, PhoneNumber &num )input.ignore(); input setw( 4 ) num.areaCode; input.ignore( 2 ); input setw( 4 ) num.exchange; input.ignore(); input setw( 5 ) num.line; return input; private: char areaCode4,exchange4,line5; ; int main() PhoneNumber phone; /创建对象phone cout phone; /语句1：使用流提取运算符 cout The phone number entered was: phone endl; /语句2：使用流插入运算符 return 0;【案例8-3】编写词汇类Words重载下标操作符#include #include using namespace std;class Words char *str;public:Words (char *s) str=new charstrlen (s) +1 ; strcpy(str, s) ; void disp() cout str =0) word n-1 =word n-1 -32 ; /语句2：字母转化为大写 n-; word.disp () ;return 0;【案例8-4】显示和隐式调用虚函数#include using namespace std;class Base public:virtual void fun(); /fun()是虚函数private: long m_nx; ;void Base:fun()coutBase=sizeof(Base)endl;class Derived: public Base long m_ny; void fun(); /派生类的覆盖版本是私有的; void Derived:fun()coutDerived=sizeof(Derived)fun(); /指针形参隐式调用虚函数，动态绑定 void Show(Base& r)r.Base:fun(); /语句1：引用形参显式调用基类虚函数，静态绑定 void main() Base* pobjx=new Base();Derived objy;int k;coutk;if(k=1)Show(pobjx);Show(&objy); / k=1调用指针形参的Show版本else / k不等于1调用引用形参Show版本Show(*pobjx);Show(objy); Showv(objy); / Showv调用中实参是派生类对象objy,形参是基类对象objx【案例8-5】设计形状类Shape通过两级抽象基类实现统一接口#include #include using namespace std;const double PI=3.14159265358979;class Shape/声明抽象基类public: virtual void Disp() = 0; virtual float area() = 0;class TwoDShape : public Shape /抽象派生类TwoDShapepublic: virtual float perimeter() = 0;class ThreeDShape : public Shape /抽象派生类ThreeDShape public: virtual float volume() = 0;class Circle : public TwoDShapepublic: Circle(float r) : radius(r) void Disp() cout Shape is a circle.n; float perimeter() return 2*PI*radius; float area() return PI*radius*radius; private: float radius;class Rectangle : public TwoDShapepublic: Rectangle(float l, float w) : length(l),width(w) void Disp() cout Shape is a Rectangle.n; float perimeter() return 2*(length+width); float area() return length*width; private: float length,width;class Cone : public ThreeDShapepublic: Cone(float r, float h) : radius(r), height(h) void Disp() cout Shape is a Cone.n; float area()return PI*radius*(radius+sqrt(radius*radius + height*height); float volume() return PI*radius*radius*height/3; private: float radius, height;class Box : public ThreeDShapepublic: Box(float l, float w,float h) : length(l),width(w), height(h) void Disp() cout Disp();/coutperimeter(); /语句1：编译错误coutarea()Disp();/coutperimeter(); /语句2：编译错误c