友元和继承访问类成员的方式的区别

class dog{public:void shout(){cout<<"dog"<<endl;}friend class pig;dog(){dogyear=0;}~dog(){}protected:int dogyear;};class niao{public:void shout() const{cout<<"niao"<<endl;}};class dogniao:public dog, public niao{public:void set(int i){dogyear=i;}void fun(){cout<<dogyear<<endl;}};class pig{public:void shout(dog d){cout<<d.dogyear<<endl;}};int main(){dogniao d;d.dog::shout();d.set(20);d.fun();pig p;dog d1;p.shout(d1);return 0;}

对于静态成员可以访问时加：：，对于一般成员在访问时就需要对对象的成员进行访问，也就是说成员是属于对象的，而静态成员是属于类的。