1.方便扩充程序，使之不必重写整个程序
代码示例
1 #include2 #include 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 father25 {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：" <
运行结果
方案二
代码示例
1 #include2 #include 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 father25 {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：" <
结果显示
显然，方案二更好些。