C++类中的六大默认成员函数详解

class Date
{
public:
    //构造函数
	Date(int year = 2021, int month = 4, int day = 11)
	{
		_year = year;
		_month = month;
		_day = day;
	}
private:
	int _year;
	int _month;
	int _day;
};

class Date
{
public:
    //构造函数的重载：
    //无参的构造函数
	Date()
	{}
    //需要传参的构造函数
	Date(int year, int month, int day)
	{
		_year = year;
		_month = month;
		_day = day;
	}
private:
	int _year;
	int _month;
	int _day;
};

class Date
{
public:
	//下面2种和 当你不写构造函数时编译器自动生成的默认构造函数只能同时存在1种
    //无参的
	Date()
	{
		_year = 2021;
		_month = 4;
		_day = 11;
	}
    //全缺省的
	Date(int year = 2021, int month = 4, int day = 11)
	{
		_year = year;
		_month = month;
		_day = day;
	}
private:
	int _year;
	int _month;
	int _day;
};

int main()
{
    //无参时
    Date d;
    //单个参数
	Date(1);
	Date d1 = 2;//这种写法会发生隐式类型转换
    //多个参数
    Date(2021, 4, 11);
    Date d2 = {2021, 4, 11};//C++11中才支持的写法
}

class Stack
{
public:
    //构造函数
	Stack(int n = 3)
	{
		_a = (int*)malloc(sizeof(int)*n);
		_size = 0;
		_capacity = n;
	}
    //析构函数
	~Stack()
	{
		free(_a);
		_size = _capacity = 0;
	}
private:
	int* _a;
	int _size;
	int _capacity;
};

int main()
{
	Date d1(1);
	//拷贝构造函数
	Date d2(d1);  //1
	Date d3 = d1; //2
 
	return 0;
}

class Date
{
public:
	Date(int year = 2021, int month = 4, int day = 11)
	{
		_year = year;
		_month = month;
		_day = day;
	}
	//赋值运算符重载
	Date& operator=(const Date& d)
	{
		_year = d._day;
		_month = d._month;
		_day = d._day;
		return *this;
	}
private:
	int _year;
	int _month;
	int _day;
};

Date d1(1);
	Date d2(0);
	
	//赋值运算符重载
	d2 = d1;     //注意，只有2个操作数都是已经定义过的变量时，才会调用赋值运算符重载
 
	//拷贝构造函数
	Date d3(d1);

class Date
{
public:
    //取地址操作符重载
	Date* operator&()
	{
		return this;
	}
    //const取地址操作符重载
	const Date* operator&()const
	{
		return this;
	}
private:
	int _year;
	int _month;
	int _day;
};

class Date
{
public:
    //初始化列表
	Date(int year, int month, int day)
		:_year(year),
		 _month(month),
		 _day(day)
	{}
 
private:
	int _year;
	int _month;
	int _day;
};