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

 1 #include <iostream>
 2 #include <string>
 3 using namespace std;
 4 class father
 5 {
 6 protected:
 7     string name;
 8     int tall;
 9 public:
10     father(string a, int i);
11     father(){ cout << "构造基类\n"; }
12     void print(){ cout << name << "身高为" << tall << "\n"; }
13     ~father(){ cout << "释放基类对象\n"; }
14 };
15 /*-------------相当于原有程序的功能-------------*/
16 father::father(string a, int i)
17 {
18     cout << "\n在基类的构造函数内\n";
19     name = a;
20     tall = i;
21     print();
22     cout << "离开基类构造函数\n";
23 }
24 class son :public father
25 {
26 private:
27     int weight;
28 public:
29     son(string a, int i, int j);
30     void print1();
31     ~son(){ cout << "\n释放子类对象\n"; }
32 };
33 /*--------相当于在原有程序功能上增加了新的功能-----------*/
34 son::son(string a, int i, int j)
35 {
36     name = a;
37     tall = i;
38     cout << "\n在子类构造函数中\n";
39     weight = j;
40 }
41 void son::print1()
42 {
43     father::print();
44     cout << "体重：" <<weight;
45 }
46 int main()
47 {
48     son a("Mike", 180, 80);
49     a.print1();
50     cout << "\n结束了\n";
51         return 0;
52 }

运行结果

方案二

代码示例

 1 #include <iostream>
 2 #include <string>
 3 using namespace std;
 4 class father
 5 {
 6 protected:
 7     string name;
 8     int tall;
 9 public:
10     father(string a, int i);
11     father(){ cout << "构造基类\n"; }
12     void print(){ cout << name << "身高为" << tall << "\n"; }
13     ~father(){ cout << "释放基类对象\n"; }
14 };
15 /*-------------相当于原有程序的功能-------------*/
16 father::father(string a, int i)
17 {
18     cout << "\n在基类的构造函数内\n";
19     name = a;
20     tall = i;
21     print();
22     cout << "离开基类构造函数\n";
23 }
24 class son :public father
25 {
26 private:
27     int weight;
28 public:
29     son(string a, int i, int j);
30     void print1();
31     ~son(){ cout << "\n释放子类对象\n"; }
32 };
33 /*--------相当于在原有程序功能上增加了新的功能-----------*/
34 son::son(string a, int i, int j):father(a,i)//不同之处
35 {
36     //name = a;
37     //tall = i;
38     cout << "\n在子类构造函数中\n";
39     weight = j;
40 }
41 void son::print1()
42 {
43     father::print();
44     cout << "体重：" <<weight;
45 }
46 int main()
47 {
48     son a("Mike", 180, 80);
49     a.print1();
50     cout << "\n结束了\n";
51         return 0;
52 }

结果显示

显然，方案二更好些。