当某个类含有类指针成员时需注意

当某个类含有类指针成员时需注意，如果该成员时通过类的构造函数初始化的。需注意：

#include "stdafx.h"
#include 
#include 

class Third
{
public:
	Third(){printf("This is Thrid's construction!\n");}
	~Third(){printf("This is Thrid's unconstruction!\n");}

	void OutPutInfo()
	{
		printf("I am Third's member fun\n");
	}
};

class Child
{
public:
	Child(Third* &third):third_(third)
	{
		printf("This is Child's construction!\n");
	}
	~Child()
	{
		printf("This is Child's unconstruction!\n");
		if (third_)
			third_->OutPutInfo();
	}
private:
	Third* &third_;//此处应该用引用，否则，当thir被释放时，则third_并不能被置null	

};

int _tmain(int argc, _TCHAR* argv[])
{
	//printf("Hello World!\n");

	Third *thir = new Third();
	Child* child = new Child(thir);

	delete thir;
	thir = NULL;

	delete child;
	child = NULL;

	system("pause");
	return 0;
}