C / C++ / MFC

5-Nov-02 20:38

hi all,
i found this error when i include 2 header files in each other's header file. i do this since i need to call each other's functions with pointer to link to these objects.

class A
{
public:
...
..
private:
B *b;
};

class B
{
public:
...
..
private:
B *b;

};

how can i solve this problem?
thanks!!!

chaze

zecodela5-Nov-02 20:39

5-Nov-02 20:39

the class declaration should like this!

class A
{
public:
...
..
private:
B *b;
};

class B
{
public:
...
..
private:
A *a;

};

Christian Graus5-Nov-02 20:52

Christian Graus

5-Nov-02 20:52

Well, you include A, it includes B, it includes A, it includes B....

This sort of stuff messes with your build times as well. Do this:

a.h:

class b{};

class a
{
...

a.cpp:

#include "stdafx.h" // always at the top
@include "b.h"

and vice versa. You're telling the compiler that b is a class, it can worry about the rest later - this works because all you're storing is a pointer, it does not need to know any details about it until it gets to the implimentation ( the .cpp file)

Christian

No offense, but I don't really want to encourage the creation of another VB developer. - Larry Antram 22 Oct 2002

Hey, at least Logo had, at it's inception, a mechanical turtle. VB has always lacked even that... - Shog9 04-09-2002

During last 10 years, with invention of VB and similar programming environments, every ill-educated moron became able to develop software. - Alex E. - 12-Sept-2002

zecodela5-Nov-02 21:53

5-Nov-02 21:53

hi,
your solution seems don't work... the compiler complain that redefine a class...

anything wrong with me?

benjymous5-Nov-02 23:31

benjymous

5-Nov-02 23:31

don't include a.h from b.h (and vice versa)

--
Help me! I'm turning into a grapefruit!

JT Anderson6-Nov-02 10:59

JT Anderson

6-Nov-02 10:59

Close. That should be:

class b;

Not:

class b{};

The curly braces are the cause of the "Redefinition" errors.

--------
There are 10 types of people in this world. Those who know binary and those who don't.

Christian Graus6-Nov-02 11:05

Christian Graus

6-Nov-02 11:05

Thanks - that's what I get for answering off the top of my head when I am tired.

Christian

No offense, but I don't really want to encourage the creation of another VB developer. - Larry Antram 22 Oct 2002

Hey, at least Logo had, at it's inception, a mechanical turtle. VB has always lacked even that... - Shog9 04-09-2002

During last 10 years, with invention of VB and similar programming environments, every ill-educated moron became able to develop software. - Alex E. - 12-Sept-2002

zecodela6-Nov-02 17:23

6-Nov-02 17:23

yes!
thanks all!

KarstenK5-Nov-02 21:00

KarstenK

5-Nov-02 21:00

I done this before with the forward-declaration as decriped in other answers.

But after a while I most found that this is a lack of the programming & class architecture.
In all my cases I have changed it somehow to no "back referencing".

possible solution:
a) inheritence
b) merge the classes
c) Make a member

You earn visibility and avoid bugs. Suspicious | :suss:

zecodela5-Nov-02 22:00

handle list ctrl wm_vscroll

5-Nov-02 22:00

hi,

first, i don't understand "forward-declaration"...

yes, i think inheritance would be useful!

let me try!
thanks,
chaze

Steve L.5-Nov-02 20:29

Steve L.

5-Nov-02 20:29

I have a Dialog App with and it has a list control in it. I want to handle wm_vscroll in the CMyDlg class though, not in a class derived from CTreeCtrl. Everything I've tried doesn't seem to work. How can I do this?

There's always one more bug.

help: adding event handler to treeview

5-Nov-02 18:11

hi,

can someone please help me with some c++ problems?

i've created a vc++ project using visual studio .net.. my application is a sdi and is using the windows explorer style(left side using treeview and right side using listview).. i've populated my trees in the treeview already, but i don't know how to add/associate control id with event handler functions.. the visual studio .net wizard wasn't very user friendly and i can't seem to find the command in the wizard which allows me to add/associate event handler with control id.. any help is welcome.. thanx in advance.

Exponential Operator

Cpudood5-Nov-02 18:00

Cpudood

5-Nov-02 18:00

Here is the code that I am working with;

void balance(float pmt)
{
float bal_k;
int k=1;
float pay;
float i=9/12;
const int n=36;

pay=pmt;
bal_k=pay*(1-((1+i)^(k-n))/i)
}

When I compile, the compiler says that because the left hand operator of the "bal_k" expression is of type float that it is illegal. I tried forcing the expression "i" to type int but it becomes zero and then there is a divide by zero error. How can I get around this?

Re: Exponential Operator

Paul M Watt5-Nov-02 18:35

Paul M Watt

5-Nov-02 18:35

actually, your problem is that the "^" is the XOR operator in C++. You will need to use the pow() function in <math.h> in order to do exponents.

Build a man a fire, and he will be warm for a day
Light a man on fire, and he will be warm for the rest of his life!

How to get app's directory?

IGx895-Nov-02 15:49

IGx89

5-Nov-02 15:49

How do I get the directory that the main exe of my app is in? I know it's probably pretty simple, but I couldn't find anything looking through the help index Frown | :(

Re: How to get app's directory?

xipeng5-Nov-02 16:07

xipeng

5-Nov-02 16:07

GetModuleFileName

Re: How to get app's directory?

IGx895-Nov-02 16:15

IGx89

5-Nov-02 16:15

Thanks!

Re: How to get app's directory?

Anonymous6-Nov-02 0:41

Anonymous

6-Nov-02 0:41

Also try looking up GetCurrentDirectory in the MSDN help file.

LogonUser?

imran_rafique5-Nov-02 15:49

imran_rafique

5-Nov-02 15:49

any body could tell the correct perameters of logonuser function?
i am having a simple network of two computers and no domain i simple need passworad and user name to enter.

My service is running on one computer where i want to login and i want to login to the system using logonuser api or function but i could not successed yet.
plz tell mee correct parameters of it?

BOOL LogonUser(
  LPTSTR lpszUsername, 
  LPTSTR lpszDomain, 
  LPTSTR lpszPassword, 
  DWORD dwLogonType, 
  DWORD dwLogonProvider, 
  PHANDLE phToken
);

r00d0034@yahoo.com

ian mariano5-Nov-02 19:19

ian mariano

5-Nov-02 19:19

Notice this: The LogonUser function attempts to log a user on to the local computer. (LogonUser[^])

If you're trying to do that over the network, it won't work.

You could use OpenSCManager()[^] to open the SCM on the remote machine, then use the other Service Functions[^] to do things with the services on that machine.

"The greatest danger to humanity is humanity without an open mind."
- Ian Mariano - http://www.ian-space.com/

Patje5-Nov-02 21:50

Patje

5-Nov-02 21:50

Some years ago I made this sample program:

main (int argc, char **argv)<br />
{<br />
BOOL   Successful;<br />
HANDLE AccessToken;<br />
DWORD  ErrorCode;<br />
char  *BufferPtr;<br />
<br />
Successful = LogonUser (argv[1], ".", argv[2], LOGON32_LOGON_NETWORK, LOGON32_PROVIDER_DEFAULT, &AccessToken);<br />
printf ("LogonUser -> %d\n", Successful);<br />
if (!Successful)<br />
   {<br />
   ErrorCode = GetLastError();<br />
   printf ("GetLastError -> %d\n",ErrorCode);<br />
   FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM, NULL, ErrorCode,<br />
                 MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), (LPTSTR) &BufferPtr, 0, NULL );<br />
   printf ("Error String -> %s\n",BufferPtr);<br />
   free (BufferPtr);<br />
   }<br />
}

However, you should have a certain privilege before you can do this (I can't remember anymore which one it was). Othwerwise you get the following error:

LogonUser -> 0<br />
GetLastError -> 1314<br />
Error String -> A required privilege is not held by the client.

Hope this helps.

Enjoy life, this is not a rehearsal !!!

Daniel Lohmann6-Nov-02 1:32

Daniel Lohmann

6-Nov-02 1:32

1) What is the result of GetLastError()?
2) What OS version, SP you are using?

The most common mistake using LogonUser() is that it needs SE_TCB_PRIVILEGE on pre-XP systems. This privilege is (and should be!) granted only to the SYSTEM account, which means that actually only service processes are able to perform a LogonUser()

--

Daniel Lohmann

http://www.losoft.de
(Hey, this page is worth looking! You can find some free and handy NT tools there Big Grin | :-D

)