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Class Pointers not so easy...

Started by Marx2052 Oct 3, 2006 at 8:54 PM 3 replies 850+ views

Original Post

Marx2052

Oct 3, 2006 at 8:54 PM

Ok this is essentially a pointer problem but that doesn't mean switch off ;) C++ and DirectX 8.1 Program. Right i've created my classes as so: Control.h CGame* pGame; CUIClass* pUIClass; Control.cpp pGame = new CGame(); pUIClass = new CUIClass(etc, etc, pGame, etc, etc); and wish to pass the a pointer to the class into a seperate class so that i can work out an iterface based on contained values, i thought since that is a pointer to a piece of memory it'd be as simple as passing that value on creation of the class i.e.: CUIClass.h CGame *pGameLoc CUIClass.cpp CUIClass(etc, etc, pGame, etc, etc); { pGameLoc = pGame; } In theory I could then use pGameLoc to retrieve mouse data etc etc from the game class. However this is not true and from my debugging it seems i'm passing an instant of the pGame class to the CUIClass i.e. the values of the pGameLoc are the values of the class when it was passed even though i know the class is working fine since i can see my mouse moving and everything else is running smoothly. Is there a problem with pointers when declareing classes using new or am i just using the wrong combination of pointers and i've testing all the combinations that make sense and some that don't. Any help would be great thanks.

Zipster

511

Zipster

Oct 3, 2006 at 9:23 PM

What is the actual declaration of the CUIClass constructor? What you're doing (or at least trying to do) should work perfectly fine, unless of course you really are inadvertently making a copy of CGame and your CUIClass is using the copy.

Marx2052

Author

Marx2052

Oct 3, 2006 at 9:41 PM

It's created in the same way as the CGame class and in the same file, CControl.cpp.

i.e.

Control.h

CGame* pGame;
CUI* pUI;

Control.cpp

pGame = new CGame(m_pD3DDevice);
pUI = new CUI(m_pD3DDevice, pGame, &m_nScreenWidth, m_nScreenHeight);

thats the order they are created in aswell right after each other.

P.S. whats this boards code for changing text to code with a scroll bar?

Marx2052

Author

Marx2052

Oct 3, 2006 at 9:59 PM

AHHH HAA!!!

I've found the problem which really i shoulda caught earlier...

pGame = new CGame(...);

was called later i'm my program by an initilisation function which would explain the problem since a new CGame was created and the pointer stored in CUI still pointed to the old CGame.

Thanks for your help you helped me look past the "ITS A POINTER ERROR!" phase.

Bregma

1,022

Bregma

Oct 4, 2006 at 8:12 AM

Quote:
Original post by Marx2052
pGame = new CGame(...);

was called later i'm my program by an initilisation function which would explain the problem since a new CGame was created and the pointer stored in CUI still pointed to the old CGame.

Thanks for your help you helped me look past the "ITS A POINTER ERROR!" phase.

It's not a pointer error. Your use of pointers was entirely correct. It's a global variable error. Global variables are bad news. You should avoid global variables if at all possible, and it's almost always possible.

It's also an aliasing error. Aliasing is severe bad news when using pointers. Avoid pointer aliasing if at all possible, and it's always possible.

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