OK I have this: class junk { protected: int x; } class junk2 : protected junk { } When I create junk and junk 2, is the value of x the same in both or does creating an inherited class create a new seperate x for junk2.

OK I figured out that this is true. What I need to know is if there is someway to do this: I have an inherited class, but I need to use the values of certain variable of the parent class. I don''t want to create new empty variables-I want to use the ones that are in the parent allready-Is this possible?

try using a static variable?

Just tried static and it won''t work-the item from parent I need to keep the way it is is a DirectDraw structure called lpdd. Any other ideas?

Here, desing your class this way, should work.

    class A{protected: int m_iX;public:  A();  virtual ~A();};class B : public A{};    

now, m_iX is available to class B as well.

Hope this helps.

OK in your example:

A.M_iX=3;

Now B.M_iX does not = 3, I need to access the value of A.M_iX from within the inherited class. I have a function in B that needs to know what the value of A.M_iX, but its not an integer-its actually a structure and static will not work-any other ideas?

It sounds like you''re doing this:

class A
{
protected:
int x;
};

class B : public A
{
}

and then creating an instance of class A

A cA;

and then creating an instance of class B

B cB;

and then hoping x will be the same value in both. Won''t happen unless you use a static variable. If you''re using a struct, you could make the member a pointer to the struct and make that pointer static. Then the pointer would be pointing to the same struct for all of the derived classes unless you override it.

Mark Fassett
Laughing Dragon Entertainment
http://www.laughing-dragon.com

I think you might be a bit confused, could you paste your code so that I can see what you are tring to accomplish.

When you inherit , your inherited class has all the attributes and methods of it's parent class. ( Not in all circumstances, but I don't want to discuss that here. )

So, A.m_iX does in fact equal B.m_iX.

Example:

    #include <iostream>using namespace std;class TestA{protected:   int m_iTestA;public:   TestA() { m_iTestA = 0; cout << "TestA Constructed" << endl; }   TestA( int iTestA ):m_iTestA( iTestA ){ cout << "TestA Constructed" << endl; }   virtual ~TestA(){ cout << "TestA Destroyed" << endl; }};class TestB : public TestA{   int m_iTestB;public:   TestB(){ m_iTestB = 1; cout << "TestB Constructed" << endl; }   TestB( int iTestA, int iTestB ):TestA(iTestA),m_iTestB(iTestB){ cout << "TestB Constructed" << endl; }   virtual ~TestB(){ cout << "TestB Destroyed" << endl; }   void Report() {      cout << "From Test A : " << m_iTestA << endl           << "From Test B : " << m_iTestB << endl;   }};int main( int argc, char* argv[] ){   TestB* ptrB = new TestB( 10, 15 );   ptrB->Report();   delete ptrB;   return 0;}    

Result from above:

TestA Constructed
TestB Constructed
From Test A : 10
From Test B : 15
TestB Destroyed
TestA Destroyed
Press any key to continue



Edited by - AlekM on July 12, 2000 12:14:12 AM

LOL-Yes I''m a Hard Head--1st:
From Test A : 10
From Test B : 15

I need Test B to = 10 too. And yes static will do this, but this keeps happening when I compile:

class C_DDraw {

public:
static int huh;
}
Tetris.obj : error LNK2001: unresolved external symbol "public: static int C_DDraw::huh" (?huh@C_DDraw@@2HA)
Debug/Tetris.exe : fatal error LNK1120: 1 unresolved externals
Error executing link.exe.

Arghhh!

OK-Here's the code

    #include <ddraw.h>#include <mmsystem.h>class C_DDraw {public:	static int huh;	C_DDraw();	~C_DDraw();	int Init(int w, int h, int c, HWND main_window_handle);	void Destroy();	void RenderInt(int FPS);	void Flipper();	void RenderGraphic();	int GetGraphic(char *file, HWND hwnd);	  protected:	static LPDIRECTDRAWSURFACE7	*junk;	LPDIRECTDRAWSURFACE7    surface;	LPDIRECTDRAW7			lpdd;// dd object	LPDIRECTDRAWSURFACE7	lpddsback;		// dd back surface	LPDIRECTDRAWSURFACE7	lpddsprimary;  // dd primary surface	DDSURFACEDESC2			ddsd;       // a direct draw surface description struct	DDSCAPS2				ddscaps;    // a direct draw surface capabilities struct		void Error(HWND hwnd, char *ErrorMsg);		};	int C_DDraw::Init(int w, int h, int c, HWND hwnd){	huh=3;// create object and test for errorif (DirectDrawCreateEx(NULL,(VOID**)&lpdd, 					   IID_IDirectDraw7,NULL)!=DD_OK)	{	Error(hwnd, "DirectDrawCreate");	return(0);	}// set cooperation level to windowed mode normalif (lpdd->SetCooperativeLevel(hwnd,           DDSCL_FULLSCREEN |            DDSCL_EXCLUSIVE | DDSCL_ALLOWREBOOT)!=DD_OK)    {	Error(hwnd, "SetCooperationLevel");	return(0);	}// set the display modeif (lpdd->SetDisplayMode(w,h,c,0,0)!=DD_OK)   	{	Error(hwnd, "SetDisplayMode");	return(0);	}// Create the primary surfaceZeroMemory(&ddsd,sizeof(ddsd));ddsd.dwSize         = sizeof(ddsd);ddsd.dwFlags        = DDSD_CAPS | DDSD_BACKBUFFERCOUNT;ddsd.ddsCaps.dwCaps = 	DDSCAPS_PRIMARYSURFACE | DDSCAPS_FLIP | DDSCAPS_COMPLEX;ddsd.dwBackBufferCount=1;if (lpdd->CreateSurface(&ddsd,&lpddsprimary,NULL)!=DD_OK)	{	Error(hwnd, "CreateSurface");	return(0);	}ZeroMemory(&ddscaps, sizeof(ddscaps));ddscaps.dwCaps=DDSCAPS_BACKBUFFER;if (lpddsprimary->GetAttachedSurface(&ddscaps, &lpddsback)!=DD_OK)	{	Error(hwnd, "GetAttachedSurface");	return(0);	}return(1);}class C_StaticSprite  : protected C_DDraw{public:		int GetGraphic(char *file);		void RenderGraphic();protected:		LPDIRECTDRAWSURFACE7	surface;		DDSURFACEDESC2			ddsd;};int C_StaticSprite::GetGraphic(char *file){	HDC						hdc;	HBITMAP					hBitmap;		// Load the bitmap	hBitmap = (HBITMAP)LoadImage(NULL, file, IMAGE_BITMAP, 0, 0,								 LR_DEFAULTSIZE | LR_LOADFROMFILE);	if (!hBitmap)	{		return NULL;	}	// Get bitmap dimensions	BITMAP bitmap;	GetObject(hBitmap, sizeof(BITMAP), &bitmap);		// Create surface		DDSURFACEDESC2			ddsd;	// Set up the stucture with the correct details	ZeroMemory(&ddsd,sizeof(ddsd));	ddsd.dwSize = sizeof(DDSURFACEDESC2);	ddsd.dwFlags = DDSD_CAPS | DDSD_WIDTH | DDSD_HEIGHT ;	ddsd.ddsCaps.dwCaps = DDSCAPS_OFFSCREENPLAIN; 	ddsd.dwWidth = bitmap.bmWidth;	ddsd.dwHeight = bitmap.bmHeight;	// Attempt to create surface	if ((C_DDraw::lpdd->CreateSurface(&ddsd, &surface, NULL)) != DD_OK)	{		return NULL;	}	// Attempt to create surface	if (surface == NULL) 	{		// Release the bitmap and return failure to caller		DeleteObject(hBitmap);		return NULL;	} 	else 	{		// Get a device context for our surface		surface->GetDC(&hdc);		// Create a compatible device context		HDC bitmap_dc = CreateCompatibleDC(hdc);		// Blit the bitmap to the surface		SelectObject(bitmap_dc, hBitmap);		BitBlt(hdc, 0, 0, bitmap.bmWidth, bitmap.bmHeight, bitmap_dc, 0, 0, SRCCOPY);		// Release the DCs		surface->ReleaseDC(hdc);		DeleteDC(bitmap_dc);	}	// Clear bitmap 	DeleteObject(hBitmap);	// Return pointer to caller		return 1;}void C_StaticSprite::RenderGraphic(){		//THIS IS THE PROBLEM        //lpddsback needs to be the original from        //C_DDraw or it will not work         	lpddsback->Blt(NULL, surface, NULL,					DDBLT_WAIT,				       NULL);}    

Edited by - Chipcrap on July 12, 2000 12:38:30 AM