Re: Help with inheritance - C / C++ / MFC Discussion Boards

Liger_Zero_X wrote:
How about getting all Cookies in the Cookies Directory?

Use FindFirstUrlCacheEntry(), and pass "cookie:" as the first parameter.

--Mike--
Personal stuff:: Ericahist | Homepage
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----
Pinky, are you pondering what I'm pondering?
I think so Brain, but if we shaved our heads, we'd look like weasels!

I am trying to do some simple inheritance with a few classes but keep running into an error at compile time. It is error C2504, 'undefined base class'. What does this mean. My classes are defined, I think they are anyway. This is what it looks like.

class a{

};

class b : public a{

};

I am including the files as well. I am just kind of stumped.
Thanks Brian.

Make sure you include the header file of your base class in your derived class.

1. say you defined class a in "a.h" file
class a
{
};

2. In class b header file

#include "a.h"

class b: public a
{
};

Jose Cezar S. Ynion

I am trying to do some simple inheritance with a few classes but keep running into an error at compile time. It is error C2504, 'undefined base class'. What does this mean. My classes are defined, I think they are anyway. This is what it looks like.

class a{

;

class b : public a{

};

I am including the files as well. I am just kind of stumped.
Thanks Brian.

?Don't ask the same question twice. The above is missing a }, so I assume it's not the actual code. Are you including the header for the base class in the HEADER for the derived class ?

Christian

I have drunk the cool-aid and found it wan and bitter. - Chris Maunder

Yes, I am including the header files. Here is some of the original code.

#ifndef ABSTRACTFACTORY_H
#define ABSTRACTFACTORY_H
#include "concAbstFactory.h"
#include "abstractFactory.h"
#include "productA.h"
#include "productB.h"


using namespace std;

class abstractFactory{
public:

	abstractFactory(){}
	 
	productA makeProductA(){
		
		return productA();
	
	}
	productB makeProductB(){

		return productB();
	}

};


#endif

#ifndef CONCABSTFACTORY_H
#define CONCABSTFACTORY_H
#include "abstractFactory.h"
#include "productA.h"
#include "productB.h"

using namespace std;



class concAbstFactory : abstractFactory{ 
public:
	
	
	concAbstFactory(){

		cout << "Building concAbstFactory" << endl;
	}
};

#endif

Sirrius wrote:
#include "concAbstFactory.h"

There's the culprit. Get rid of that line and the sun will being to shine once more Smile | :)

Ryan

"Punctuality is only a virtue for those who aren't smart enough to think of good excuses for being late" John Nichol "Point Of Impact"

Strange. What was so wrong with that. "concAbstFactory.h" is another class that I am going to need to derive other classes from later. Hmmm.
Getting rid of it did help though. Thanks for your eagle eye.
Brian.

Sirrius wrote:
Strange. What was so wrong with that.

Ok, say we're trying to compile abstractFactory.h... The compiler starts the pass, and hits the #include "concAbstFactory.h" statement, so opens the file and starts to process it, where it finds the line #include "abstractFactory.h". When it opens this file, it gets caught by your #ifndef (since the file is already included), and skips over the file. Returning to the concAbstFactory.h file, it tries to process the class definition but since it hasn't reaches the declaration of abstractFactory yet, it complains that the base class is not defined, which is correct. So basically, the compiler is seeing the lines in this order:

/* abstractFactory.h */
#ifndef ABSTRACTFACTORY_H
#define ABSTRACTFACTORY_H
#include "concAbstFactory.h"
    /* concAbstFactory.h */
    #ifndef CONCABSTFACTORY_H
    #define CONCABSTFACTORY_H
    #include "abstractFactory.h
        /* abstractFactory.h */
        #ifndef ABSTRACTFACTORY_H
        #endif                       // Skips over everything in between since the definition is now true
    /* concAbstFactory.h */
    #include "productA.h"
    #include "productB.h"
    using namespace std;
    class concAbstFactory : abstractFactory

...etc...

See the problem?

Ryan

"Punctuality is only a virtue for those who aren't smart enough to think of good excuses for being late" John Nichol "Point Of Impact"

Hi Sirrius,

The problem was very well described by Ryan.

The solution to fix your compilation error is to delete both #include statements.

Here is an example of a simple yet correct way to include header files like your are trying to do:

File ClassA.h:

#ifndef CLASSA_H
#define CLASSA_H
#include "ClassB.h" // <- Remove this line
#include "ClassA.h" // <- Remove this line
class a
{ ... };
#endif

File ClassB.h:

#ifndef CLASSB_H
#define CLASSB_H
#include "ClassA.h" // Include definition of base class.
class b : public a
{ ... };
#endif

If you want to derive other classes from concAbstFactory then simply include "concAbstFactory.h" in the header files for those new derived classes. Your base classes should not have any knowledge of your derived classes.

Hope this helps. Smile | :)

Eric

In the file that defines class abstractFactory, you're including the file that defines class concAbstFactory:

#include "concAbstFactory.h"

concAbstFactory is derived from abstractFactory (which hasn't yet been defined at this point), so there's your hiccup. Remove the include statement mentioned above and try again.

Including the headers of child classes in their base class should make you nervous.

Please pardon the redundant response. I failed to read further into the thread before replying.

Hi
I just installed STLPort on my system, and I find it superior to Dinkumware's implementation of STL. However, I am now building a library that will be used by a lot of users, and not all of them have STLPort on their system. Is there a way that I can build my library and still make it usable on all systems?

Thanks!

Any STL implimentation is going to be in the form of code that you include. So it's already in your program, the compiler puts it there.

Christian

I have drunk the cool-aid and found it wan and bitter. - Chris Maunder

Hi
I wanna capture the desktop and save it to a jpg file, I know how to save it to a bmp file uncompressed but that file is to large 3 megs!!.

So I try to modify the code for capturing to an bmp

and I can not view the jpgs I create

what is wrong?

where am I wrong

here is the code:
[code]

#include <windows.h>
// C RunTime Header Files
#include <stdlib.h>
#include <malloc.h>
#include <memory.h>
#include <tchar.h>

// TODO: reference additional headers your program requires here
#include <shellapi.h>
#include <commdlg.h>

int APIENTRY WinMain(HINSTANCE hInstance,
HINSTANCE hPrevInstance,
LPSTR lpCmdLine,
int nCmdShow)
{
static HBITMAP hDesktopCompatibleBitmap=NULL;
static HDC hDesktopCompatibleDC=NULL;
static HDC hDesktopDC=NULL;
static HWND hDesktopWnd=NULL;

hDesktopWnd=GetDesktopWindow();
hDesktopDC=GetDC(hDesktopWnd);
hDesktopCompatibleDC=CreateCompatibleDC(hDesktopDC);
hDesktopCompatibleBitmap=CreateCompatibleBitmap(hDesktopDC,GetSystemMetrics(SM_CXSCREEN),GetSystemMetrics(SM_CYSCREEN));
SelectObject(hDesktopCompatibleDC,hDesktopCompatibleBitmap);

OPENFILENAME ofn;
char szFileName[512]; szFileName[0]='\0';
ZeroMemory(&ofn,sizeof(ofn));
ofn.lStructSize=sizeof(OPENFILENAME);
ofn.Flags=OFN_HIDEREADONLY|OFN_PATHMUSTEXIST;
ofn.lpstrFilter="JPEG Files (*.jpg)\0*.jpg\0";
ofn.lpstrDefExt="jpg";
ofn.lpstrFile=szFileName;
ofn.nMaxFile=512;
if(!GetSaveFileName(&ofn));

BitBlt(hDesktopCompatibleDC,0,0,GetSystemMetrics(SM_CXSCREEN),GetSystemMetrics(SM_CYSCREEN),hDesktopDC,0,0,SRCCOPY);

BITMAPINFO bi;
void *pBits=NULL;
int nWidth=GetSystemMetrics(SM_CXSCREEN);
int nHeight=GetSystemMetrics(SM_CYSCREEN);
ZeroMemory(&bi,sizeof(bi));
bi.bmiHeader.biSize=sizeof(bi.bmiHeader);
bi.bmiHeader.biHeight=nHeight;
bi.bmiHeader.biWidth=nWidth;
bi.bmiHeader.biPlanes=1;
bi.bmiHeader.biBitCount=0;
bi.bmiHeader.biCompression=BI_JPEG;
bi.bmiHeader.biSizeImage=3*nWidth*nHeight;

HDC hBmpFileDC=CreateCompatibleDC(hDesktopCompatibleDC);

StretchDIBits(hBmpFileDC,
// destination rectangle
0,0 ,GetSystemMetrics(SM_CXSCREEN), GetSystemMetrics(SM_CYSCREEN),
// source rectangle
0, 0, nWidth, nHeight,
pBits,
&bi,
DIB_RGB_COLORS,
SRCCOPY);

HANDLE hFile=CreateFile(szFileName,GENERIC_WRITE,FILE_SHARE_WRITE,NULL,CREATE_ALWAYS,FILE_ATTRIBUTE_NORMAL,NULL);
if(hFile!=INVALID_HANDLE_VALUE)
{
DWORD dwRet=0;
BITMAPFILEHEADER bmfHeader;
ZeroMemory(&bmfHeader,sizeof(bmfHeader));
bmfHeader.bfOffBits=sizeof(BITMAPFILEHEADER)+sizeof(BITMAPINFOHEADER);
bmfHeader.bfSize=bi.bmiHeader.biSizeImage+bmfHeader.bfOffBits;
bmfHeader.bfType='MB';

WriteFile(hFile,&bmfHeader,sizeof(bmfHeader),&dwRet,NULL);
WriteFile(hFile,&bi.bmiHeader,sizeof(bi.bmiHeader),&dwRet,NULL);
WriteFile(hFile,pBits,bi.bmiHeader.biSizeImage,&dwRet,NULL);
CloseHandle(hFile);
}

DeleteDC(hBmpFileDC);

return 0;
}
[/code]

also if anyone knows how to save an ico to a file after I get it's handle please tell me

I need to know

Spiritofamerica wrote:
also if anyone knows how to save an ico to a file after I get it's handle please tell me

http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&threadm=%23k5tXe9RBHA.1424%40tkmsftngp03&rnum=3&prev=/&frame=on

--
Dad, how strange it is that the pig can speak.
*thoughtful pause* It must have lost its "oink".
(my 3-year old daughter Moa, while watching Babe)

Human beings, who are almost unique in having the ability
to learn from the experience of others, are also remarkable
for their apparent disinclination to do so. (Douglas Adams)

Spiritofamerica wrote:
also if anyone knows how to save an ico to a file after I get it's handle please tell me

Google?

--
Dad, how strange it is that the pig can speak.
*thoughtful pause* It must have lost its "oink".
(my 3-year old daughter Moa, while watching Babe)

Human beings, who are almost unique in having the ability
to learn from the experience of others, are also remarkable
for their apparent disinclination to do so. (Douglas Adams)

anyone any ideas why a slider that increased values as it moved left to right now decreases as the slider is moved from bottom to top? I just changed it from horizontal to vertical through the properties box under msdv6.......shouldnt it increase as the slider is moved up?

cant find an option to rotate/flip it.

If it works anything like a spin button control, the arrows will act reversed until you set the range over which the control is suppost to work after that they should be the correct way up.

Try using the SetRange() function. Also try swapping over the min/max values

If you vote me down, my score will only get lower

Hi I'm kinda new so i'm sorry if i'm ask this in the wrong forum.

I would like to know if it's possible to get the processID of a process that has terminated another process.
Is it possible to get this ID in the process that is (going to be) terminated and/or is it possible to get the ID from a third process that is running at that time.

I searched on Google already, i searched on the MSDN @ MS online, and ofcourse on The Code Project, but I couldn't find anything useful Frown | :(

Although i must say, i find it a hard subject to make a good search on.

Tnx Big Grin | :-D

Loading...

Hi
I wanna capture the desktop and save it to a jpg file, I know how to save it to a bmp file uncompressed but that file is to large 3 megs!!.

So I try to modify the code for capturing to an bmp

and I can not view the jpgs I create

what is wrong?

where am I wrong

here is the code:
[code]

#include <windows.h>
// C RunTime Header Files
#include <stdlib.h>
#include <malloc.h>
#include <memory.h>
#include <tchar.h>

// TODO: reference additional headers your program requires here
#include <shellapi.h>
#include <commdlg.h>

int APIENTRY WinMain(HINSTANCE hInstance,
HINSTANCE hPrevInstance,
LPSTR lpCmdLine,
int nCmdShow)
{
static HBITMAP hDesktopCompatibleBitmap=NULL;
static HDC hDesktopCompatibleDC=NULL;
static HDC hDesktopDC=NULL;
static HWND hDesktopWnd=NULL;

hDesktopWnd=GetDesktopWindow();
hDesktopDC=GetDC(hDesktopWnd);
hDesktopCompatibleDC=CreateCompatibleDC(hDesktopDC);
hDesktopCompatibleBitmap=CreateCompatibleBitmap(hDesktopDC,GetSystemMetrics(SM_CXSCREEN),GetSystemMetrics(SM_CYSCREEN));
SelectObject(hDesktopCompatibleDC,hDesktopCompatibleBitmap);

OPENFILENAME ofn;
char szFileName[512]; szFileName[0]='\0';
ZeroMemory(&ofn,sizeof(ofn));
ofn.lStructSize=sizeof(OPENFILENAME);
ofn.Flags=OFN_HIDEREADONLY|OFN_PATHMUSTEXIST;
ofn.lpstrFilter="JPEG Files (*.jpg)\0*.jpg\0";
ofn.lpstrDefExt="jpg";
ofn.lpstrFile=szFileName;
ofn.nMaxFile=512;
if(!GetSaveFileName(&ofn));

BitBlt(hDesktopCompatibleDC,0,0,GetSystemMetrics(SM_CXSCREEN),GetSystemMetrics(SM_CYSCREEN),hDesktopDC,0,0,SRCCOPY);

BITMAPINFO bi;
void *pBits=NULL;
int nWidth=GetSystemMetrics(SM_CXSCREEN);
int nHeight=GetSystemMetrics(SM_CYSCREEN);
ZeroMemory(&bi,sizeof(bi));
bi.bmiHeader.biSize=sizeof(bi.bmiHeader);
bi.bmiHeader.biHeight=nHeight;
bi.bmiHeader.biWidth=nWidth;
bi.bmiHeader.biPlanes=1;
bi.bmiHeader.biBitCount=0;
bi.bmiHeader.biCompression=BI_JPEG;
bi.bmiHeader.biSizeImage=3*nWidth*nHeight;

HDC hBmpFileDC=CreateCompatibleDC(hDesktopCompatibleDC);

StretchDIBits(hBmpFileDC,
// destination rectangle
0,0 ,GetSystemMetrics(SM_CXSCREEN), GetSystemMetrics(SM_CYSCREEN),
// source rectangle
0, 0, nWidth, nHeight,
pBits,
&bi,
DIB_RGB_COLORS,
SRCCOPY);

HANDLE hFile=CreateFile(szFileName,GENERIC_WRITE,FILE_SHARE_WRITE,NULL,CREATE_ALWAYS,FILE_ATTRIBUTE_NORMAL,NULL);
if(hFile!=INVALID_HANDLE_VALUE)
{
DWORD dwRet=0;
BITMAPFILEHEADER bmfHeader;
ZeroMemory(&bmfHeader,sizeof(bmfHeader));
bmfHeader.bfOffBits=sizeof(BITMAPFILEHEADER)+sizeof(BITMAPINFOHEADER);
bmfHeader.bfSize=bi.bmiHeader.biSizeImage+bmfHeader.bfOffBits;
bmfHeader.bfType='MB';

WriteFile(hFile,&bmfHeader,sizeof(bmfHeader),&dwRet,NULL);
WriteFile(hFile,&bi.bmiHeader,sizeof(bi.bmiHeader),&dwRet,NULL);
WriteFile(hFile,pBits,bi.bmiHeader.biSizeImage,&dwRet,NULL);
CloseHandle(hFile);
}

DeleteDC(hBmpFileDC);

return 0;
}

[/code]

Sorry, how did you expect this code to save a jpg ?

The best and easiest way is to use GDI+.

Christian

I have drunk the cool-aid and found it wan and bitter. - Chris Maunder

In answer to your email, my articles on GDI+ are not the only ones here that will show you have to save a jpg with GDI+.

Christian

I have drunk the cool-aid and found it wan and bitter. - Chris Maunder

I am planning to use Named Events to provide a scripting interface to my application.

The scripting DLL would fire these Events, say Check box 1 checked etc.

My question is how many Named Events can an application deal with without any problems.
i.e. 1 ~10; 10 ~100; 100 ~ 500 etc.

I thought that Events would provide a nice clean interface; rather than using memory mapped files/mutux protected etc.

Any comments?

grahamfff

You can make hundreds, but you have to ask yourself, would you want to?
You can only wait on, I think, 32 at a time with WaitForMultipleObjects, so having so many events might not be a good solution to your design problem.

It might be better to have a few in several classes, like 'data ready' and 'abort' and a few others. Then find some scheme to generate a queue that you can put command or data items into to be read by your 'processor' when a particular event is set.

If you want to proivde a scripting interface to your application, can't you just embed visual basic for applications, make an OLE Automation Interface, or implement local RPC calls for example?