C++_练习—多态_纯虚函数与抽象类

纯虚函数与抽象类

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含有纯虚函数的类，称为抽象基类，不可实列化。即不能创建对象，存在的意义就是被继承，提供族类的公共接口。

 

// 纯虚函数与抽象类

#include <iostream>

using namespace std;

class shape {
public:
    virtual double getarea() = 0;
};

class cfx :public shape {
public:
    cfx(int a, int b) {
        this->a = a;
        this->b = b;
    }

    virtual double getarea() {
        cout << "cfx =  " << a*b << endl;
        return a * b ;
    }

private:
    int a;
    int b;
};

class yx :public shape {
public:
    yx(int r) {
        this->r = r;
    }

    virtual double getarea() {
        cout << "yx =  " <<  3.14*r*r << endl;
        return 3.14*r*r;
    }

private:
    int r;
};

int main(void)
{
    shape *changfx = new cfx(2,3);
    changfx->getarea();

    shape *yuan = new yx(1);
    yuan->getarea();

    system("pause");

    return 0;
}

 

 

笔记

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