C++友元函数和友元类的使用详解

#include <iostream>
using namespace std;
class Student{
public:
    Student(char *name, int age, float score); //构造函数
public:
    friend void show(Student *pstu);  //将show()声明为类Student的友元函数
private:
    char *m_name;
    int m_age;
    float m_score;
};
Student::Student(char *name, int age, float score): m_name(name), m_age(age), m_score(score){ }
//非成员函数
void show(Student *pstu){
    cout<<pstu->m_name<<"的年龄是 "<<pstu->m_age<<"，成绩是 "<<pstu->m_score<<endl;
}
int main(){
    Student stu("小明", 15, 90.6);
    show(&stu);  //调用友元函数
    Student *pstu = new Student("李磊", 16, 80.5);
    show(pstu);  //调用友元函数
    return 0;
}

shennd void show(Student *pstu);  //将show()声明为类Student的友元函数

void show(Student *pstu){
    cout<<pstu->m_name<<"的年龄是 "<<pstu->m_age<<"，成绩是 "<<pstu->m_score<<endl;
}

#include <iostream>
using namespace std;
class Address;  //提前声明Address类
//声明Student类
class Student{
public:
    Student(char *name, int age, float score);
public:
    void show(Address *addr);
private:
    char *m_name;
    int m_age;
    float m_score;
};
//声明Address类
class Address{
private:
    char *m_province;  //省份
    char *m_city;  //城市
    char *m_district;  //区（市区）
public:
    Address(char *province, char *city, char *district);
    //将Student类中的成员函数show()声明为友元函数
    friend void Student::show(Address *addr);
};
//实现Student类
Student::Student(char *name, int age, float score): m_name(name), m_age(age), m_score(score){ }
void Student::show(Address *addr){
    cout<<m_name<<"的年龄是 "<<m_age<<"，成绩是 "<<m_score<<endl;
    cout<<"家庭住址："<<addr->m_province<<"省"<<addr->m_city<<"市"<<addr->m_district<<"区"<<endl;
}
//实现Address类
Address::Address(char *province, char *city, char *district){
    m_province = province;
    m_city = city;
    m_district = district;
}
int main(){
    Student stu("小明", 16, 95.5f);
    Address addr("陕西", "西安", "雁塔");
    stu.show(&addr);
   
    Student *pstu = new Student("李磊", 16, 80.5);
    Address *paddr = new Address("河北", "衡水", "桃城");
    pstu -> show(paddr);
    return 0;
}

friend void Student::show(Address *addr);

class Address{
public:
Address(char *province, char *city, char *district);
public:
//将Student类声明为Address类的友元类
friend class Student;
private:
char *m_province; //省份
char *m_city; //城市
char *m_district; //区（市区）
};