14.类模板与友元

#include<iostream>
using namespace std;

//掌握类模板配合友元函数的类内和类外实现

//全局函数类内实现-直接在类内声明友元即可
//全局函数类外实现-需要提前让编译器知道全局函数的存在


//1.类外实现先声明模板类的存在
template<class T1, class T2>
class PERSON;

//2.全局函数类外实现
template<class T1, class T2>
void PrintPerson1(PERSON<T1, T2> p)
{
    cout << "姓名：" << p.m_Name << endl;
    cout << "年龄：" << p.m_Age << endl;
}

template<class T1,class T2>
class PERSON
{
    //全局函数类内实现
    friend void PrintPerson(PERSON<T1,T2> p)
    {
        cout << "姓名：" << p.m_Name << endl;
        cout << "年龄：" << p.m_Age << endl;
    }

    //3.全局函数类外实现
    //加空模板参数列表
    //如果全局函数是类外实现，需要让编译器提前知道这个函数的存在
    friend void PrintPerson1<>(PERSON<T1, T2> p);

public:
    PERSON(T1 name,T2 age)
    {
        this->m_Name = name;
        this->m_Age = age;
    }

private:

    T1 m_Name;
    T2 m_Age;
};


void test14()
{
    //全局函数在类内实现
    PERSON<string, int>p("xiansifan",22);
    
    PrintPerson(p);


    //全局函数在类外实现
    PERSON<string, int>p1("hello", 23);
    PrintPerson1(p1);
}
int main()
{

    test14();

    system("pause");
    return 0;
}