继承的作用以及在子类中初始化所有数据的方法

1.方便扩充程序，使之不必重写整个程序

代码示例

#include <iostream>
#include <string>
using namespace std;
class father
{
protected:
    string name;
    int tall;
public:
    father(string a, int i);
    father(){ cout << "构造基类
"; }
    void print(){ cout << name << "身高为" << tall << "
"; }
    ~father(){ cout << "释放基类对象
"; }
};
/*-------------相当于原有程序的功能-------------*/
father::father(string a, int i)
{
    cout << "
在基类的构造函数内
";
    name = a;
    tall = i;
    print();
    cout << "离开基类构造函数
";
}
class son :public father
{
private:
    int weight;
public:
    son(string a, int i, int j);
    void print1();
    ~son(){ cout << "
释放子类对象
"; }
};
/*--------相当于在原有程序功能上增加了新的功能-----------*/
son::son(string a, int i, int j)
{
    name = a;
    tall = i;
    cout << "
在子类构造函数中
";
    weight = j;
}
void son::print1()
{
    father::print();
    cout << "体重：" <<weight;
}
int main()
{
    son a("Mike", 180, 80);
    a.print1();
    cout << "
结束了
";
        return 0;
}

运行结果

方案二

代码示例

#include <iostream>
#include <string>
using namespace std;
class father
{
protected:
    string name;
    int tall;
public:
    father(string a, int i);
    father(){ cout << "构造基类
"; }
    void print(){ cout << name << "身高为" << tall << "
"; }
    ~father(){ cout << "释放基类对象
"; }
};
/*-------------相当于原有程序的功能-------------*/
father::father(string a, int i)
{
    cout << "
在基类的构造函数内
";
    name = a;
    tall = i;
    print();
    cout << "离开基类构造函数
";
}
class son :public father
{
private:
    int weight;
public:
    son(string a, int i, int j);
    void print1();
    ~son(){ cout << "
释放子类对象
"; }
};
/*--------相当于在原有程序功能上增加了新的功能-----------*/
son::son(string a, int i, int j):father(a,i)//不同之处
{
    //name = a;
    //tall = i;
    cout << "
在子类构造函数中
";
    weight = j;
}
void son::print1()
{
    father::print();
    cout << "体重：" <<weight;
}
int main()
{
    son a("Mike", 180, 80);
    a.print1();
    cout << "
结束了
";
        return 0;
}

结果显示

显然，方案二更好些。