C++ Primer Plus学习笔记之拷贝构造函数

In constructor...

Point Count=1

In Fun()...

Point Count=1,此时已经出错了，因为此时内存中不仅存在着p1对象，还存在着临时对象形参p;

After object destroyed...

Point Count=0

After Point2 create...

Point Count=0

After object destroyed...

Point Count=-1

After object destroyed...

Point Count=-2

解决问题的方法相当直观，就是为Point类提供一个显示 的拷贝构造函数。

#include

using namespace std;

class Point
{
	public:
		Point(int ix=0,int iy=0)
		{
			x=ix;
			y=iy;
			PtCount++;
			PrintCount("In constructor...");
		}
		Point(const Point &p)//拷贝构造函数
		{
			x=p.x;
			y=p.y;
			PtCount++;
			PrintCount("In copy constructor...");
		}
		~Point()
		{
			PtCount--;
			PrintCount("After object destroyed...");
		}
		static void PrintCount(const char *str)
		{
			cout运行结果：


In constructor...
Point Count=1       p1形成
..........................................................
In copy constructor...
Point Count=2
In Fun()...
Point Count=2      形参p拷贝实参p1的结果
.........................................................
In copy constructor...
Point Count=3      p2接受Fun返回的结果
........................................................
After object destroyed...
Point Count=2      形参p销毁
........................................................
After Point2 create...
Point Count=2      p2形成
........................................................
After object destroyed...
Point Count=1      p2销毁
........................................................
After object destroyed...
Point Count=0    
p1销毁
.........................................................