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Newbie Question

Started by Antion Dec 23, 2001 at 1:17 AM 0 replies 500+ views

Original Post

Dec 23, 2001 at 1:17 AM

Ok, which graphic API is better Direct X or Open Gl (just kidding) Actually my question is this. I am currently learning C++ (from like 3 different books) and the one question that I am coming up with is with Conversion Constructors and Member Conversion Functions. What exactly are they used for. Ok, the books say to make an object of one type to another but what would you use that for? I know this is probably a very naive question, but it is something that I haven't found in any of my books. One example in my book converts a Xmas object to a DayOfYear object, this example really doesn't get across the idea. What am I missing? Thanks ~Antion Edited by - antion on December 23, 2001 2:17:42 AM Edited by - antion on December 23, 2001 2:30:25 AM

Shannon Barber

Mod

368

Shannon Barber

Dec 23, 2001 at 1:43 AM

It''s most useful for utility classes, classes that wrap-up something you use or do alot.

This is a simple class I made to make dealing with events trivial. But in order to use my class in-place of a Windows Event handle, it needs to be able to convert itself into a HANDLE. That''s what operator HANDLE() does.

  
	class CEvent
		{
		public:
			enum eResetMode {AutoReset=FALSE, ManualReset=TRUE};
			CEvent(eResetMode ResetMode=AutoReset, BOOL bInitialState=FALSE, LPSECURITY_ATTRIBUTES pSecAtr=NULL, LPCTSTR szName=NULL) : m_hEvent(0)
				{
				m_hEvent = CreateEvent(pSecAtr, bManualReset, bInitialState, szName);
				assert(m_hEvent);
				}
			
			CEvent(HANDLE hEvent) : m_hEvent(hEvent)
				{
				}
			
			CEvent(const CEvent& cEvent)
				{
				m_hEvent = cEvent.m_hEvent;
				}
			
			~CEvent()
				{
				if(m_hEvent)
					CloseHandle(m_hEvent);
				}
			
			operator HANDLE()
				{
				assert(m_hEvent);
				return(m_hEvent);
				}
			
			HANDLE* operator&()
				{
				assertMsg(m_hEvent==NULL, "This usually indicates a bug");
				return &m_hEvent;
				}
			
			BOOL Signal()
				{
				assert(m_hEvent);
				return SetEvent(m_hEvent);
				}
			
			BOOL Reset()
				{
				assert(m_hEvent);
				return ResetEvent(m_hEvent);
				}
			
			BOOL Pulse()
				{
				assert(m_hEvent);
				return PulseEvent(m_hEvent);
				}
		public:
			HANDLE m_hEvent;
		};

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