C++句柄代码实现(1)

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http://blog.csdn.net/tanhuifang520

C++句柄代码实现(1)

C++句柄

作用：解决代理类中，创建代理时复制所有代理对象的问题

#include 
using namespace std;

class Point{
	public:
		Point():xval(0){}
		Point(int _x):xval(_x){}
		Point &x(int _x){ xval = _x; return *this;}
		int x(){ return xval; }
	private:
		int xval;
};

class UPoint{
	    // 所有成员为私有
		friend class Handle;
		UPoint():u(1){}
		UPoint(int _x):u(1),P(_x){}
		UPoint(Point &p0):u(1),P(p0){}
		int u;
		Point P;
};

class Handle{
	public:
		Handle():up(new UPoint){}
		Handle(int _x):up(new UPoint(_x)){}
		Handle(Point &p0):up(new UPoint(p0)){}
		Handle(Handle &h):up(h.up){ up->u++; }
		~Handle(){ if(0 == --up->u) delete up;}
		Handle& operator=(const Handle &h)
		{
			if(0 == --up->u)
				delete up;
			
			up = h.up;
			up->u++;
		}
		int x()
		{
			return up->P.x();
		}
#if 1	
		// 指针语义
		Handle& x(int _x)
		{
			up->P.x(_x);
			return *this;
		}
		
#else
		// 值语义
		Handle& x(int _x)
		{
			if(1 != up->u)
			{
				up->u--;
				up = new UPoint(up->P);
			}
			up->P.x(_x);
			return *this;
		}
#endif
	private:		
		UPoint *up;
};


int main()
{
	Handle h(3);
	Handle h1 = h;
	h1.x(5);
	cout<<"h.x = "<