运算符重载

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加号运算符

1.成员函数承载运算符

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class Person
{
public:

	//成员函数重载运算符
	Person operator+(Person& p)
	{
		Person t;
		t.m_A = this->m_A + p.m_A;
		t.m_B = this->m_B + p.m_B;
		
		return t;
	}


	int m_A;
	int m_B;
};
//成员函数重载+的本质：p3=p1.operator+(p2)

2.全局函数重载运算符

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//全局函数重载加号
Person operator+(Person& p1, Person& p2)
{
	Person t;
	t.m_A = p1.m_A+ p2.m_A;
	t.m_B = p1.m_B + p2.m_B;

	return t;
}
//全局函数重载本质调用：p3=operator+(p1,p2)

ps：运算符重载也可以发生函数重载

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void test01()
{
	Person p1;
	Person p2;
	p1.m_A = 10;
	p1.m_B = 10;
	p2.m_A = 10;
	p2.m_B = 10;
	
	Person p3 = p1 + p2;
}

左移运算符重载

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class Person
{
	friend ostream& operator<<(ostream& cout, Person& p);//友元函数 访问私有变量
public:
	Person(int a, int b)
	{
		m_A = a;
		m_B = b;
	}
private:	
	int m_A;
	int m_B;
};

//只能用全局函数重载左移运算符
//cout输出流对象只能有一个,所以要用引用的方式
ostream& operator<<(ostream &cout,Person &p)
{
	cout << "m_A=" << p.m_A << "m_B=" << p.m_B;


	return cout;
}

void test01()
{
	Person p(10, 10);

	cout << p << endl;
}

递增运算符重载

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class MyInteger
{
	friend ostream& operator<<(ostream& cout, MyInteger myint);

public:
	MyInteger()
	{
		m_Num = 0;
	}

	//重载++运算符 前置
	//返回引用是为了一直对一个数据进行操作
	MyInteger& operator++()
	{
		m_Num++;
		return *this;
	}
	
	//重载++运算符 后置
	//返回值 而不是引用
	MyInteger operator++(int) //int 代表占位参数，可以用于区分前置和后置
	{
		MyInteger temp = *this;
		m_Num++;

		return temp;
	}
private:
	int m_Num;
};

//左移运算符重载
ostream& operator<<(ostream& cout, MyInteger myint)
{
	cout << myint.m_Num;
	return cout;
}

void test01()
{
	MyInteger myint;

	cout << ++myint << endl;//输出1
}

void test02()
{
	MyInteger myint;

	cout << myint++ << endl;//输出0
	cout << myint << endl;//输出1
}

赋值运算符重载

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class Person
{
public:
	Person(int age)
	{
		m_Age = new int(age);
	}

	~Person()
	{
		if (m_Age != NULL)
		{
			delete m_Age;
			m_Age = NULL;
		}
	}

	Person& operator=(Person& p)
	{
		//先判断是否有属性在堆区，如果有先释放干净，再进行深拷贝
		if (m_Age != NULL)
		{
			delete m_Age;
			m_Age = NULL;
		}
		//深拷贝
		m_Age = new int(*p.m_Age);
		return *this;
        //this是一个指向当前对象的指针，类型为Person*
        //*this表示当前对象本身（而不是指针）
	}

	int* m_Age;
};

void test01()
{
	Person p1(18);
	Person p2(20);
	Person p3(30);

	p3 = p2 = p1;//因为重载时的返回类型是对象的引用，所以可以连续运算

	cout << "p1的年龄" << *p1.m_Age;
	cout << "p1的年龄" << *p2.m_Age;
}

关系运算符

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class Person
{
public:
	Person(string name, int age)
	{
		m_Name = name;
		m_Age = age;
	}

	bool operator==(Person& p)
	{
		if (this->m_Name == p.m_Name && this->m_Age == p.m_Age)
		{
			return true;
		}

		return false;
	}

	string m_Name;
	int m_Age;
};

函数调用运算符重载

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class MyPrint
{
public:

	void operator()(string test)
	{
		cout << test << endl;
	}
};

void test01()
{
	MyPrint myPrint;
	myPrint("hello world");//执行这条语句 会有输出：hello world
	//由于使用起来非常类似于函数调用，因此称为仿函数
}

//仿函数非常灵活，没有固定写法
//加法类
class MyAdd
{
public:
	int operator()(int num1, int num2)
	{
		return num1 + num2;
	}
};

void test02()
{
	MyAdd myadd;
	int ret = myadd(100, 100);

	//匿名对象的调用 类名()
	cout << MyAdd()(100, 100) << endl;
}