模板类的友元重载

#include<iostream>

using namespace std;

template<class T>

class Test;

template<class T>

ostream& operator<<(ostream& out, const Test<T> &obj);

template <class T>

class Test

{

private:

int num;

public:

Test(int n = 0)

{

num = n;

}

Test(const Test<T>& copy)

{

num = copy.num;

}

friend ostream& operator<< <>

(ostream& out, const Test<T> &obj);

//注意在“<<”后加上"<>"表明这是个函数模板

};

template<class T> ostream& operator<<(ostream& out, const Test<T> &obj)

{

out << obj.num;

return out;

}

int main()

{

Test<int> t(2);

cout << t;

return 0;

}