C++ Primer笔记13_运算符重载_总结

总结：

1.不能重载的运算符: . 和 .* 和 ?: 和 ::  和 sizeof 和 typeid

2.重载运算符有两种基本选择: 类的成员函数或者友元函数, 建议规则例如以下:

运算符	建议使用
全部一元运算符	成员函数
＝ () [] ->	必须是成员函数
+= -= /= *= ^= &= != %= >>= <<= , 似乎带等号的都在这里了.	成员函数
全部其他二元运算符, 比如: –,+,*,/	友元函数

3.前几篇中的实例，如今汇总Person类的程序：

#include <iostream>
#include <new>
#include <string>

using namespace std;

class Person
{
public:
	Person();
	Person(int n, const string &str);
	Person(const Person &n);
	Person &operator=(const Person &p);
	~Person();

	string getName()const;
	friend ostream &operator<<(ostream &out, const Person &p);
	friend istream &operator>>(istream &in, Person &p);
	friend Person operator+(const Person &p1, const Person &p2);
	friend bool operator==(const Person &p1, const Person &p2);
	Person & operator++();
	Person & operator--();
	Person & operator++(int);
	Person & operator--(int);
	Person * operator->();
	Person & operator*();
private:
	int age;
	string *name;
};

Person::Person():age(0), name(NULL)
{
	cout << "Default Person" << endl;
}

Person::Person(int n, const string &str):age(n), name(new string(str))
{
	cout << "Init Person" << endl;
}

Person::Person(const Person &n)
{
	if(n.name)
	{
		name = new string(*(n.name));
		age = n.age;
	}
	else
	{
		name = NULL;
		age = 0;
	}
}

Person & Person::operator=(const Person &p)
{
	if(this == &p)
	{
		return *this;
	}
	string *tmp = new string(*p.name);
	delete this->name;
	this->name = tmp;
	this->age = p.age;

	cout << "operator =" << endl;

	return *this;
}

Person::~Person()
{
	cout << "~Person " << "name: " << name << " age: " << age << endl;
	delete name;
}

string Person::getName()const
{
	if(name)
	{
		return *name;
	}
	return string();
}

ostream &operator<<(ostream &out, const Person &p)
{
	out << "p.age: " << p.age << ", p.name: " << p.getName();
	return out;
}

istream &operator>>(istream &in, Person &p)
{
	string s;
	cout << "please input age and name:";
	in >> p.age >> s;
	if(in)
	{
		p.name = new string(s);
	}
	else
	{
		p = Person();
	}

	return in;
}

Person operator+(const Person &p1, const Person &p2)
{
	string s1(*p1.name);
	string s2(*p2.name);
	Person p;
	p.age = p1.age + p2.age;
	p.name = new string(s1+s2);
	return p;
}

bool operator==(const Person &p1, const Person &p2)
{
	if(p1.age == p2.age && p1.name == p2.name)
	{
		return true;
	}
	return false;
}

Person & Person::operator++()
{
	age++;//only ++ age
	return *this;
}

Person & Person::operator--()
{
	age--;
	return *this;
}

Person & Person::operator++(int)
{
	Person &p = *this;
	age++;
	return p;
}

Person & Person::operator--(int) 
{
	Person &p = *this;
	age--;
	return p;
}

Person * Person::operator->()
{
	return this;
}

Person & Person::operator*()
{
	return *this;
}


int main()
{
	Person p1(20, "SCOTT");
	Person p2(10, "Kate");

	cout << p1->getName() << endl;
	cout << (*p2).getName() << endl;
	
	return 0;
}

到此，运算符重载先告一段落，以后还会继续探究更深层次的问题。