#include<string>
using namespace std;
class Student;
class Class
{
private:
int id;
string student_name;
public:
//因爲現在還沒有具體聲明Student類,所以我們要把函數的實現放在Student類的聲明後面
void show(const Student& s); //因爲Class是Student的友元類,所以可以直接訪問Student的私有數據
void student_show(const Student&); //即使Class不是Student類的友元類,這個函數也可以訪問Student類的私有數據,因爲它是Student類的友元成員函數
};
class Student
{
private:
string name;
int age;
int grade;
int clas;
public:
friend class Class; //友元類的聲明可以放在類中任何地方
Student(string name_, int age_, int grade_, int clas_):name(name_), age(age_), grade(grade_), clas(clas_){}
friend ostream& operator<<(ostream& os, const Student& s) //友元函數
{
os << s.name << " " << s.age << " " << s.grade << " " << s.clas << endl;
return os;
}
friend void Class::student_show(const Student&); //友元成員函數
};
void Class::show(const Student& s) //因爲Class是Student的友元類,所以可以直接訪問Student的私有數據
{
cout << s.name << " " << s.clas << endl;
}
void Class::student_show(const Student& s)
{
cout << s.name << " " << s.age << " " << s.grade << " " << s.clas << endl;
}
int main()
{
//友元函數
Student s1("linukey", 20, 100, 1);
cout << s1;
//友元類
Class c1;
c1.show(s1);
//友元成員函數
c1.student_show(s1);
cin.get();
return 0;
}