C++运算符重载（二）之左移运算符重载

class Person {

public:

	Person(int a, int b)
	{
		this->m_A = a;
		this->m_B = b;
	}
	//利用成员函数实现左移运算符：p.operator<<(cout)简化版本p << cout 无法实现cout在左边。
	//成员函数 p << p 不是我们想要的效果，想要cout<<p
	void operator<<(Person& p){
    	cout << "a:" << p.m_A << " b:" << p.m_B;
	}

private:
	int m_A;
	int m_B;
};

void test() {

	Person p1(10, 20);
	p1 << p1;//p1.operator<<(p1);
}

int main() {

	test();

	system("pause");

	return 0;
}

class Person {
    //全局函数做友元，告诉编译器 operator<<全局函数 是 Person类的好朋友，可以访问类中的私有内容
	friend void operator<<(ostream& out, Person& p);

public:

	Person(int a, int b)
	{
		this->m_A = a;
		this->m_B = b;
	}

private:
	int m_A;
	int m_B;
};

//只能全局函数实现左移重载
//ostream对象只能有一个
void operator<<(ostream& out, Person& p) {
	out << "a:" << p.m_A << " b:" << p.m_B;
}

void test() {

	Person p1(10, 20);
	cout << p1;
}

int main() {

	test();

	system("pause");

	return 0;
}

class Person {
	friend ostream& operator<<(ostream& out, Person& p);

public:

	Person(int a, int b)
	{
		this->m_A = a;
		this->m_B = b;
	}
private:
	int m_A;
	int m_B;
};

//只能全局函数实现左移重载
//ostream对象只能有一个,所以添加&取地址,cout的定义类型为ostream
ostream& operator<<(ostream& out, Person& p) {
	out << "a:" << p.m_A << " b:" << p.m_B;
	return out;//返回cout需要更改函数头为ostream
}

void test() {

	Person p1(10, 20);

	cout << p1 << "hello world" << endl; //链式编程。
}

int main() {

	test();

	system("pause");

	return 0;
}