父类调用子类
#include <iostream>

using namespace std;


class Animal {
public:
    virtual void cry(){
        cout << "Animal Cry" << endl;
    }

    void name(){
        cout << "Animal Name " << endl;
    }
};

class Dog : public Animal {
public:
    virtual void cry(){
        cout << "Dog Cry" << endl;
    }

    void name(){
        Animal::name(); // 子类可以使用父类的  反过来不行
        cout << "Dog Name " << endl;
    }

};
例子2

方法实现

class Rectangle {

public:
    int x = 5;
    int y = 10;
    int area(int x,int y);
    int girth(int x,int y);

};

int Rectangle::area(int x, int y) {
    return x*y;
}

int Rectangle::girth(int x, int y) {
    return 2* (x+y);
}

int main(){

    Rectangle *rectangle = new Rectangle();
    int area = rectangle->area(10,20);
    cout << "area=" << area << endl;

    return 1;
}
例子3

使用变量

class Rectangle {

public:
    int x = 5;
    int y = 10;
    int area(int x,int y);
    int girth(int x);

};

int Rectangle::area(int x, int y) {
    return x*y;
}

int Rectangle::girth(int x) {
    return 2* (x+Rectangle::y); //Rectangle::y
}

int main(){


    Rectangle *rectangle = new Rectangle();

    int area = rectangle->area(10,20);
    cout << "area=" << area << endl;

    int girth = rectangle->girth(5);
    cout << "girth=" << girth << endl;

    return 1;
}