[C++知识库]C++友元与输出运算符重载

#pragma once
#include <ostream>
#include <iostream>
using namespace std;

class MyComplex {
public:
	int GetA() const{
		return a;
	}
	int GetB() const {
		return b;
	}

	//输出重载一
	friend ostream& operator < (ostream& out, const MyComplex& com);//注意ostream前不能加const，因为流要插入修改

	//输出重载二
	ostream& operator > (ostream& out) {
		out << "operator>" << a << ", " << b;
		return out;
	}

	static void TestFriend();


private:
	int a=0, b=10;
};

//友元函数，是全局函数
ostream& operator < (ostream& out, const MyComplex& com) {
	out << "operator<" << com.a << ", " << com.b;
	return out;
}

//输出重载三，全局函数
ostream& operator << (ostream& out, const MyComplex& com) {
	out << "operator<<" << com.GetA() << ", " << com.GetB();
	return out;
}


//测试用例
void MyComplex:: TestFriend() {
	MyComplex complex;

	//下面2种调用等价
	operator <<(std::cout, complex) << endl;
	std::cout << complex << std::endl;

	//下面2种调用等价
	(std::cout < complex) << endl; //加括号因为<<优先级高于<
	(operator <(std::cout, complex)) << endl; //友元函数是全局函数

	//下面2种调用等价
	(complex > std::cout) << endl;
	(complex.operator>(std::cout)) << endl;

	/*输出结果：
	*	operator<<0, 10
		operator<<0, 10
		operator<0, 10
		operator<0, 10
		operator>0, 10
		operator>0, 10
	*/

}