区分接口继承和实现继承

 1 class Airplane{
 2 public:
 3     virtual void fly(const Airport& destination) = 0;
 4 };
 5 void Airplane::fly(const Airport& destination){ //纯虚函数的实现
 6     缺省行为
 7 }
 8 class mA :public Airplane{
 9 public:
10     virtual void fly(const Airport& destination){
11         Airplane::fly(destination);
12     }
13 };