目录

• 1 博客内容
• 2 代码_继承

1 博客内容

      之前看C++特性，不知所然，今天得空回顾以下，似有所或。

      参考B站视频和RUNOOB，码字记录。

2 代码_继承

      子类可以自动继承父类方法(public)和属性(private),包括构造函数(无参数的构造函数)。父类中private更改为protected,主函数不能访问,但是派生类能访问。

#include <iostream>
using namespace std;
class Box
{
  public:
    double get_volume(void);
    void set(double l, double b, double h);
    Box();                             //无参数的构造函数
    Box(double a, double b, double c); //可以更改变量的构造函数,重构函数
  protected:
    double length;  // 长度
    double breadth; // 宽度
    double height;  // 高度
};
Box::Box()
{
    length = 0.0;
    breadth = 0.0;
    height = 0.0;
}
double Box::get_volume(void)
{
    return length * breadth * height;
}
void Box::set(double len, double bre, double hei)
{
    length = len;
    breadth = bre;
    height = hei;
}
///Box_wood(木箱子类)来自box类公有(方法)派生
// class Box_wood: public Box{
// }
class Box_wood : public Box
{
  public:
    Box_wood();
    Box_wood(double l, double w, double h, string m);
    double Box_wood_get_weight();
    void Box_wood_set(double len, double wit, double hei, string mat);
  private:
    /* data */
    string materia;
};
Box_wood::Box_wood()
{
    Box();
    materia = "wood";
}
Box_wood::Box_wood(double l, double w, double h, string m) //有写法,加上:Box(double l,double h)
{
    //这里不能定义 height =h;  //子类能继承,但是不能使用构造函数修改父类已经构造的属性???
    //构造即为初始化,对父类属性初始化,2次没有必要
    length = l;
    height = h;
    height = h;
    materia = m;
}
void Box_wood::Box_wood_set(double len, double wit, double hei, string mat)
{
    set(len, wit, hei);
    materia = mat;
}
double Box_wood::Box_wood_get_weight()
{
    double density(0.0);
    double volume(0.0);
    if (materia == "wood")
    {
        /* code */
        density = 0.9;
    }
    else
    {
        density = 0;
    }
    volume = get_volume();
    return density * volume;
}
int main()
{
    Box father_box;
    cout << "结果输入如下:" << endl;
    cout << "father_box的构造体积" << father_box.get_volume() << endl;
    father_box.set(1.1, 1.2, 3.2);
    cout << "father_box的设置体积" << father_box.get_volume() << endl;
    Box_wood a;
    cout << "子类a的构造体积" << a.get_volume() << endl;
    double weight_1(0.0);
    a.Box_wood_set(4.0, 5.0, 5.0, "wood");
    // a.set(16.0, 8.0, 12.0);
    //不能cout箱子的长宽高,即私有成员变量在main函数中看不到.
    weight_1 = a.Box_wood_get_weight();
    cout << "a 的重量：" << weight_1 << endl;
    return 0;
}