C / C++ / MFC

11-May-08 21:30

Hey everybody,
I got problem with prototype. I do have 2 classes both inherited from CDialog. And these two have pointer, which points each other.
It seems smt like this:

<br />
CChild : CDialog<br />
{<br />
CMain* parent;<br />
<br />
void doSmt();<br />
};<br />
<br />
CMain : CDialog<br />
{<br />
CChild* child;<br />
<br />
void doSmt();<br />
};<br />

I got a header file which includes Child first and Main after. OK now my problem is
if I do not write class prototype of Main in the header file before including Child header file it gives me error: CMain undeclared identifier which makes sense.
But, when I do write prototype:

<br />
class CMain;<br />
<br />
#include "CChild.h"<br />
#include "CMain.h"<br />

then it gives me use of undefined type CMain at the line which I call a function of CMain from CChild class.

And when I do (try to) write a prototype of DoSmt function:

<br />
class CMain;<br />
void CMain::doSmt();<br />
<br />
#include "CChild.h"<br />
#include "CMain.h"<br />

gives me the same error at line where I define function prototype.

So I guess the question is, how can I define prototype of my class function Confused | :confused:

Thanks.... Smile | :)

CPallini11-May-08 21:41

11-May-08 21:41

dehseth wrote:
class CMain;

#include "CChild.h"
#include "CMain.h"

then it gives me use of undefined type CMain at the line which I call a function of CMain from CChild class.

What is the source file compiling (whenever this error occurs)?

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

dehseth11-May-08 22:23

11-May-08 22:23

source code is a lil bit long it makes more confusion if I paste it in here.

this error occurs during compiling:

I have 2 classes which points each other with pointers.
During compile I include child.h first and main.h later.
Since child class includes a main class pointer in itself it asks for the class. So I need to write a prototype for mainclass before including child class. When I write class CMain; it asks for Main class functions, cause child class calls function of main class. And here my problem starts cause compiler says undeclare identifier of CMain class...

So how can I declare a working prototype of CMain class to compile whole code Confused | :confused:

CPallini11-May-08 22:50

11-May-08 22:50

Deferred declaration (the one you used for class CMain should work, but you've define methods containing references to CMain methods inside CChild source (not inside the header).

for instance:

//FILE: B.h
class A;
class B 
{
  A * _pA;

  B(pA){_pA=pA;}
  void DoSomethingWithA();
};
//////////////////////////////////
//FILE B.cpp
void B::DoSomethingWithA()
{
  _pA->DoSomething();
}

should work, while

//FILE: B.h
class A;
class B
{
A * _pA;

B(pA){_pA=pA;}
void DoSomethingWithA()
{
_pA->DoSomething(); // ERROR, UNDEFINED REFERENCE
}
};

shouldn't.

Smile | :)

dehseth12-May-08 1:35

12-May-08 1:35

ok! I got a lil bit confused right now... You sound right. I need to include header files.. Well I did writye the source code bottom of header files which is wrong, I get that now!

Now my problem continues... These are the files I have got:

Main.cpp
Child.cpp
MSFLexGrid.cpp
Application.cpp

I include header files in each of them correctly. Compling each one one by one does not create any errors. But when I do Build, if says

error LNK2005: "int __cdecl getSize(char *)" (?getSize@@YAHPAD@Z) already defined in App.obj

cause it's already included in cpp file... So Do I have to write

#ifndef

directives to each header file Confused | :confused:

How can I build without having any linker errors??
Thanks... Smile | :)

CPallini12-May-08 2:08

12-May-08 2:08

How did you define such function? Where?

dehseth12-May-08 2:55

12-May-08 2:55

ok I have solved the problem!

I've got linker error problems because I am defining Message Map declerations in header file.

I just move BEGIN_MESSAGE_MAP parts into cpp file and my problem is solved! Laugh | :laugh:

Thank you for your help! Smile | :)

Rajkumar R11-May-08 21:43

Rajkumar R

11-May-08 21:43

you need the forward declaration in the declaration file, say in CMain.h,
declare

CMain.h:
class CChild; // forward declaration.
CMain : CDialog
{
CChild* child;

void doSmt();
};

remove the forward declaration in the cpp(I Suppose)

CMain.cpp:

dehseth wrote:

~~class CMain;~~

#include "CMain.h"
#include "CChild.h"

void CMain::doSmt()
{
}

#include "CChild.h"
#include "CMain.h"

dehseth11-May-08 22:16

11-May-08 22:16

didn't worked.....still says undeclared identifier.. Cry | :((

MFC Problem with writing file

Rajkumar R11-May-08 22:27

Rajkumar R

11-May-08 22:27

yes that can happen for the other CChild.cpp,
if you understand what forward declaration can do, you can alone fix the problem.
if you want from me, say what are the files cpp, h and how you declare

mihai12311-May-08 21:16

mihai123

11-May-08 21:16

Hello ,
I use this section to write some code in a file
f.Open(_T("file.log"), CFile::modeNoTruncate | CFile::modeWrite);
if(f!=f.hFileNull)
{
f.SeekToEnd();
}
else
{
f.Open(szFilename, CFile::modeCreate | CFile::modeWrite);
}
CArhive arStore(&f, CArchive::store);
arStore.WriteString(_T("message");

It works fine like this. But I want to make a class that writes the file.
In .h I have :
private:
CFile f;
CArchive arStore;
And I have a method to write an open file.
I encounter a problem in constructing the arStore object. (ERROR: CArchive not apropiate default constructor available)
This like is the problem : arStore(&f, CArchive::store);

I think that there is a method like Open for CFile but I don't find it.

Tnx for the help

Re: MFC Problem with writing file

Naveen11-May-08 21:25

Naveen

11-May-08 21:25

mihai123 wrote:
I encounter a problem in constructing the arStore object. (ERROR: CArchive not apropiate default constructor available)

You can use the Initialization list.

eg:

class Test
{

private: 
   CFile f;
   CArchive arStore;
public:
  Test():arStore(&f, CArchive::store)
   {
   };
};

nave

[OpenedFileFinder]

Re: MFC Problem with writing file

mihai12311-May-08 22:10

mihai123

11-May-08 22:10

tnx it works Smile | :)

Skin

john563211-May-08 21:06

john5632

11-May-08 21:06

Hi,

How can I add skin to my project?

Re: Skin

Hamid_RT11-May-08 21:10

Hamid_RT

11-May-08 21:10

Do you need to these articles
here[^] and here[^]?

Re: Skin

Rajesh R Subramanian11-May-08 22:53

Rajesh R Subramanian

11-May-08 22:53

Your question is bringing me too many things to assume. Before I assume anything wild, have you searched Google?

Nobody can give you wiser advice than yourself. - Cicero
.·´¯`·->Rajesh<-·´¯`·.
Codeproject.com: Visual C++ MVP

CreateThread and AfxBeginThread

tom groezer11-May-08 20:54

tom groezer

11-May-08 20:54

In MFC what is the difference between these functions and what is the fine line calling AfxBeginThread vs calling ::CreateThread

Hamid_RT11-May-08 21:17

Hamid_RT

11-May-08 21:17

See here[^].

CPallini11-May-08 21:20

11-May-08 21:20

The documentation ([^] and [^]) doesn't help, does it?
Roughly speaking, you can spot the main difference in the AfxBeginThread overloaded form supporting user interface threads, i.e.:

CWinThread* AfxBeginThread(
   CRuntimeClass* pThreadClass,
   int nPriority = THREAD_PRIORITY_NORMAL,
   UINT nStackSize = 0,
   DWORD dwCreateFlags = 0,
   LPSECURITY_ATTRIBUTES lpSecurityAttrs = NULL 
);

The above provides some boiler plate code helping, user interface threads development.
Smile | :)

ShilpiP11-May-08 22:55

ShilpiP

11-May-08 22:55

MSDN
Use AfxBeginThread to create a thread object and execute it in one step. Use CreateThread if you want to reuse the thread object between successive creation and termination of thread executions.

Yes U Can ...If U Can ,Dream it , U can do it ...ICAN