[C++]纯虚函数

任何包含一个或者多个的纯虚函数都叫做抽象类,因此不能对它实例化.否则会导致编译错误;

从抽象类继承而来的类若不覆盖纯虚函数,依然是纯虚函数,所以派生类务必覆盖纯虚函数

纯虚函数定义

可以到我这一篇源代码

#include <iostream>
using namespace std;
#define PI 3.1415926
class Shape
{
public:
    virtual void Print()=0;
    virtual float Area()=0;

}; 
class Circle: public Shape
{
    float R;
public:
    Circle(float R);
    void Print();
    float Area();
};

Circle::Circle(float R)
{
    this->R=R;
}

void Circle::Print()
{
    cout<<"the R of this Circle is "<<R<<endl;
}

float Circle::Area()
{
    return PI*R*R;
}



class Rectangle:public Shape
{
    float length,width;
public:
    Rectangle(float length,float width);
    void Print();
    float Area();
};

Rectangle::Rectangle(float length,float width)
{
    this->length=length;
    this->width=width;
}
void Rectangle::Print()
{
    cout<<"the length is "<<length<<endl<<"the width is "<<width<<endl; 
}
float Rectangle::Area()
{
    return length*width;

}
int main()
{
    Shape *S;
    S = new Circle(10);
    S->Print();
    cout<<"the Area of the Circle is "<<S->Area()<<endl;
    delete S;
    S = new Rectangle(10,5);
    S->Print();
    cout<<"the Area of the Rectangle is "<<S->Area()<<endl;
    int n;
    cin>>n;
    return 0;
}

作者: 林羽飞扬
出处：http://www.cnblogs.com/zhengyuhong/
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