c++常见的运算符重载
重载运算符作用：对已有的运算符进行重新定义，赋予其另一种功能，以适应不同的数据类型
1.加号运算符重载
#include <iostream>
using namespace std;
#include <string>
class Person
{
public:
int m_A;
int m_B;
// Person operator+(Person &p)
// {
// Person temp;
// temp.m_A = m_A + p.m_A;
// temp.m_B = m_B + p.m_B;
// return temp;
// }
};
Person operator+(Person &p1, Person &p2)
{
Person temp;
temp.m_A = p1.m_A + p2.m_A;
temp.m_B = p1.m_B + p2.m_B;
return temp;
}
Person operator+(Person &p1, int num)
{
Person temp;
temp.m_A = p1.m_A + num;
temp.m_B = p1.m_B + num;
return temp;
}
void test()
{
Person p1;
p1.m_A = 10;
p1.m_B = 20;
Person p2;
p2.m_A = 10;
p2.m_B = 20;
Person p3 = p1 + p2;
cout << "p3 m_A = " << p3.m_A << endl;
cout << "p3 m_B = " << p3.m_B << endl;
Person p4 = p1 + 100;
cout << "p4 m_A = " << p4.m_A << endl;
cout << "p4 m_B = " << p4.m_B << endl;
}
int main()
{
test();
return 0;
}
2.左移运算符重载
作用：输出自定义数据类型
#include <iostream>
using namespace std;
#include <string>
class Person
{
public:
int m_A;
int m_B;
};
ostream &operator<<(ostream &cout, Person &p)
{
cout << p.m_A << " " << p.m_B << endl;
return cout;
}
void test()
{
Person p;
p.m_A = 10;
p.m_B = 10;
cout << p << "hello world" << endl;
}
int main()
{
test();
return 0;
}
3.递增运算符重载
作用：通过重载递增运算符，实现自定义数据整形相加
#include <iostream>
using namespace std;
#include <string>
class MyInteger
{
friend ostream &operator<<(ostream &cout, MyInteger my);
public:
MyInteger()
{
m_num = 0;
}
MyInteger &operator++()
{
++m_num;
return *this;
}
MyInteger operator++(int)
{
MyInteger temp = *this;
m_num++;
return temp;
}
private:
int m_num;
};
//前置++运算符
ostream &operator<<(ostream &cout, MyInteger my)
{
cout << my.m_num;
return cout;
}
void test()
{
MyInteger myint;
cout << ++(++myint) << endl;
cout << myint << endl;
}
void test2()
{
MyInteger myint;
cout << myint++ << endl;
cout << myint << endl;
}
int main()
{
test();
// test2();
return 0;
}
4.赋值运算符重载
C++编译器默认至少给一个类添加4个函数
- 默认构造函数（无参，函数体为空）
- 默认析构函数（无参，函数体为空）
- 默认拷贝构造函数，对属性值进行拷贝
- 赋值运算符 operator=,对属性进行值拷贝
如果类中有属性指向堆区，做赋值操作时也会导致深浅拷贝问题
基础类型的
#include <iostream>
using namespace std;
#include <string>
class Person
{
public:
Person(int age)
{
m_Age = age;
}
int m_Age;
};
void test()
{
Person p1(18);
cout << "p1 =="<<p1.m_Age<<endl;
Person p2(20);
p1 = p2;
cout << "p1 =="<<p1.m_Age<<endl;
}
int main()
{
test();
system("pause");
return 0;
}
对象类型的
涉及到深浅拷贝问题
#include <iostream>
using namespace std;
#include <string>
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)
{
this->m_Age = new int(*p.m_Age);
return *this;
}
int *m_Age;
};
void test()
{
Person p1(18);
cout << "p1 ==" << *p1.m_Age << endl;
Person p2(20);
Person p3(22);
p1 = p2 = p3;
cout << "p1 ==" << *p1.m_Age << endl;
}
int main()
{
test();
system("pause");
return 0;
}
5.关系运算符重载
作用：重载关系运算符，可以让两个自定义的对象进行比较
#include <iostream>
using namespace std;
#include <string>
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;
}
bool operator!=(Person &p)
{
if (this->m_Name == p.m_Name && this->m_Age == p.m_Age)
{
return false;
}
return true;
}
string m_Name;
int m_Age;
};
void test()
{
Person p1("Tom", 18);
Person p2("Jerry", 18);
if (p1 == p2)
{
cout << "p1 和 P2是相等的！" << endl;
}
else
{
cout << "p1 和 P2是不相等的！" << endl;
}
if (p1 != p2)
{
cout << "p1 和 P2是不相等的！" << endl;
}
else
{
cout << "p1 和 P2是相等的！" << endl;
}
}
int main()
{
test();
system("pause");
return 0;
}
6.函数调用运算符重载
- 函数调用运算符也可以重载
- 由于重载后，使用很想函数的调用，所以被称为仿函数
- 仿函数没有固定写法，非常灵活
#include <iostream>
using namespace std;
#include <string>
class MyPrint
{
public:
void operator()(string txt)
{
cout << txt << endl;
}
int operator()(int num1, int num2)
{
return num1 + num2;
}
};
void test01()
{
MyPrint myPrint;
myPrint("hello world"); //看着像函数，实际不是
MyPrint()("Hello World"); //匿名仿函数
int num = myPrint(100, 300);
cout << num << endl;
}
int main()
{
test01();
return 0;
}