关于接口继承和实现继承：
所谓接口继承，就是派生类只继承函数的接口，也就是声明；而实现继承，就是派生类同时继承函数的接口和实现。
纯虚函数：要求继承类必须含有某个接口，并对接口函数实现。 虚函数：继承类必须含有某个接口，可以自己实现，也可以不实现，而采用基类定义的缺省实现。 非虚函数：继承类必须含有某个接口，必须使用基类的实现。关于飞机问题代码如下：
#include <iostream>
#include <cstring>
using namespace std;
class Airport
{
public:
Airport(){}
Airport(char *p)
{
int len=strlen(p);
delete [] des;
des=NULL;
des=new char[len+1];
strcpy(des,p);
}
Airport(const Airport& Ap )
{
int len=strlen(Ap.des);
delete [] des;
des=NULL;
des=new char[len+1];
strcpy(des,Ap.des);
}
void SetDestination(char *p)
{
int len=strlen(p);
delete [] des;
des=NULL;
des=new char[len+1];
strcpy(des,p);
}
Airport& operator=(const Airport& Ap )
{
if (this==&Ap)
return *this;
int len=strlen(Ap.des);
delete [] des;
des=NULL;
des=new char[len+1];
strcpy(des,Ap.des);
return *this;
}
void show() const//这里一定要加const，因为若不加const，在调用destination.show()时会报错，
//因为destination为const Airport的引用
{
cout<<"The destination is :"<<des<<endl;
}
private:
char* des;
};
class Airplane
{
public:
virtual void fly(const Airport& destination);
};
void Airplane::fly(const Airport& destination)
{
destination.show();
}
class ModelA:public Airplane
{
};
class ModelB:public Airplane
{
};
class ModelC:public Airplane
{
};
int main()
{
Airport PDX("ChengDu");
Airplane* pa=new ModelC;
pa->fly(PDX);
Airplane* pb=new ModelA;
pb->fly(PDX);
return 0;
}
由于C也为声明fly函数，所以会调用缺省的的Airplane：：fly，从而本该飞行方式不同的C采用了和A、B相同的飞行方式；
#include <iostream>
#include <cstring>
using namespace std;
class Airport
{
public:
Airport(){}
Airport(char *p)
{
int len=strlen(p);
delete [] des;
des=NULL;
des=new char[len+1];
strcpy(des,p);
}
Airport(const Airport& Ap )
{
int len=strlen(Ap.des);
delete [] des;
des=NULL;
des=new char[len+1];
strcpy(des,Ap.des);
}
void SetDestination(char *p)
{
int len=strlen(p);
delete [] des;
des=NULL;
des=new char[len+1];
strcpy(des,p);
}
Airport& operator=(const Airport& Ap )
{
if (this==&Ap)
return *this;
int len=strlen(Ap.des);
delete [] des;
des=NULL;
des=new char[len+1];
strcpy(des,Ap.des);
return *this;
}
void show() const//这里一定要加const，因为若不加const，在调用destination.show()时会报错，
//因为destination为const Airport的引用
{
cout<<"The destination is :"<<des<<endl;
}
private:
char* des;
};
class Airplane
{
public:
virtual void fly(const Airport& destination)=0;
};
void Airplane::fly(const Airport& destination)
{
destination.show();
}
class ModelA:public Airplane
{
};
class ModelB:public Airplane
{
};
class ModelC:public Airplane
{
};
int main()
{
Airport PDX("ChengDu");
Airplane* pa=new ModelC;
pa->fly(PDX);
Airplane* pb=new ModelA;
pb->fly(PDX);
return 0;
}
可是如果将类Airplane中的fly声明为纯虚函数，虽然有定义，但是此时ModelA等就不能缺省了，因为
纯虚函数最突出的特产就是它必须被任何继承了它们的类重新声明，通常纯虚函数在抽象类没有定义，但是也可以定义，但是调用它的唯一途径是“调用时明确指出其类的名称”如下所示：
#include <iostream>
#include <cstring>
using namespace std;
class Airport
{
public:
Airport(){}
Airport(char *p)
{
int len=strlen(p);
delete [] des;
des=NULL;
des=new char[len+1];
strcpy(des,p);
}
Airport(const Airport& Ap )
{
int len=strlen(Ap.des);
delete [] des;
des=NULL;
des=new char[len+1];
strcpy(des,Ap.des);
}
void SetDestination(char *p)
{
int len=strlen(p);
delete [] des;
des=NULL;
des=new char[len+1];
strcpy(des,p);
}
Airport& operator=(const Airport& Ap )
{
if (this==&Ap)
return *this;
int len=strlen(Ap.des);
delete [] des;
des=NULL;
des=new char[len+1];
strcpy(des,Ap.des);
return *this;
}
void show() const//这里一定要加const，因为若不加const，在调用destination.show()时会报错，
//因为destination为const Airport的引用
{
cout<<"The destination is :"<<des<<endl;
}
private:
char* des;
};
class Airplane
{
public:
virtual void fly(const Airport& destination)=0;
};
void Airplane::fly(const Airport& destination)
{
destination.show();
}
class ModelA:public Airplane
{
virtual void fly(const Airport& destination)
{
cout<<"ModelA"<<endl;
Airplane::fly(destination);
}
};
class ModelB:public Airplane
{
virtual void fly(const Airport& destination)
{
cout<<"ModelB"<<endl;
Airplane::fly(destination);
}
};
class ModelC:public Airplane
{
virtual void fly(const Airport& destination)
{
cout<<"ModelC"<<endl;
Airplane::fly(destination);
}
};
int main()
{
Airport PDX("ChengDu");
Airplane* pa=new ModelC;
cout<<"1: "<<endl;
pa->Airplane::fly(PDX);
cout<<"2: "<<endl;
pa->fly(PDX);
return 0;
}
