Click here to Skip to main content
11,642,233 members (64,494 online)
Click here to Skip to main content

Using AfxBeginThread with class member controlling function

, 19 Jun 2002 CPOL 221.4K 2.8K 26
Rate this:
Please Sign up or sign in to vote.
Create worker threads with class member controlling function

Introduction

Creating a separate thread in your application in order to execute some time consuming operations is very simple. You just call AfxBeginThread() with the appropriate parameters and that's it. But Microsoft wants the controlling function either to be a global function or to be a static class member function; which in both cases means that you don't have access to your class member variables or methods from within the controlling function. This article shows you a little trick on how to do this and keep your source OO.

Step-by-Step

  1. Create your project as usual, add your dialogs, controls and all the stuff.
  2. Create your classes for the dialogs using Class Wizard, and assign variables to your controls.
  3. For the class you want to implement multithreading, edit the header file adding the following code:
    //controlling function header
    static UINT StartThread (LPVOID param);
    
    //structure for passing to the controlling function
    typedef struct THREADSTRUCT
    {
        CThreadDemoDlg*    _this;
            //you can add here other parameters you might be interested on
    } THREADSTRUCT;
  4. In the implementation file for your class, add the following code:
    UINT CThreadDemoDlg::StartThread (LPVOID param)
    {
        THREADSTRUCT*    ts = (THREADSTRUCT*)param;
    
        //here is the time-consuming process 
        //which interacts with your dialog
        AfxMessageBox ("Thread is started!");
    
            //see the access mode to your dialog controls
        ts->_this->m_ctrl_progress.SetRange (0, 1000);  
        while (ts->_this->m_ctrl_progress.GetPos () < 1000)
        {
            Sleep(500);
            ts->_this->m_ctrl_progress.StepIt ();
        }
    
        //you can also call AfxEndThread() here
        return 1;
    }
    void CThreadDemoDlg::OnStart() 
    {
            //call the thread on a button action or menu
        THREADSTRUCT *_param = new THREADSTRUCT;
        _param->_this = this;
        AfxBeginThread (StartThread, _param);
    }
  5. Now you can test your program!

Conclusion

I hope this will be helpful for you. I've been using CodeProject for a long time and this article is the first step for payback.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Share

About the Author

Enis
Software Developer (Senior)
Romania Romania
No Biography provided

You may also be interested in...

Comments and Discussions

 
GeneralWonderful! Thanks a lot Pin
claxcss1-Oct-14 21:37
memberclaxcss1-Oct-14 21:37 
GeneralMy vote of 1 Pin
sunilkpv28-Nov-12 20:27
membersunilkpv28-Nov-12 20:27 
GeneralMy vote of 1 Pin
Panic2k318-Sep-09 17:57
memberPanic2k318-Sep-09 17:57 
GeneralTHREADSTRUCT Not Needed Pin
Jonathan Wood4-Feb-09 4:33
memberJonathan Wood4-Feb-09 4:33 
GeneralDon't use this "trick" Pin
Roland_W5-Nov-08 11:01
memberRoland_W5-Nov-08 11:01 
GeneralGreat trick, thanks!! Pin
philbnt5-May-08 22:04
memberphilbnt5-May-08 22:04 
QuestionMulti Client Server Please Help! Pin
MauraV13-Oct-07 18:42
memberMauraV13-Oct-07 18:42 
QuestionUsing this method with a other class. Pin
CVianney9-Oct-07 22:25
memberCVianney9-Oct-07 22:25 
GeneralThank you very much Pin
Member #31823345-Feb-07 16:31
memberMember #31823345-Feb-07 16:31 
GeneralHelp for OpenGL Thread Pin
srinin00824-Jul-06 3:59
membersrinin00824-Jul-06 3:59 
GeneralAlso on memory leak Pin
chiac2-Apr-06 18:46
memberchiac2-Apr-06 18:46 
GeneralThanks Pin
dhammeriz12-Dec-05 7:09
memberdhammeriz12-Dec-05 7:09 
GeneralMemory leak on THREADSTRUCT Pin
srev21-Jun-05 2:54
membersrev21-Jun-05 2:54 
GeneralRe: Memory leak on THREADSTRUCT Pin
Anonymous19-Oct-05 2:45
sussAnonymous19-Oct-05 2:45 
GeneralRe: Memory leak on THREADSTRUCT Pin
ciyoung16-Feb-06 17:36
memberciyoung16-Feb-06 17:36 
GeneralUnhandled Exception Pin
Anonymous26-May-04 2:44
sussAnonymous26-May-04 2:44 
GeneralStop Thread Pin
aman20066-May-04 5:57
memberaman20066-May-04 5:57 
GeneralRe: Stop Thread Pin
Enis6-May-04 6:34
memberEnis6-May-04 6:34 
GeneralRe: Stop Thread Pin
j.v.r.25-Aug-10 7:47
memberj.v.r.25-Aug-10 7:47 
GeneralStop Thread Problem Pin
aman20065-May-04 14:52
memberaman20065-May-04 14:52 
GeneralHELP PLEASE Pin
win32newb3-Mar-04 17:01
memberwin32newb3-Mar-04 17:01 
GeneralRe: HELP PLEASE Pin
Jens Winslow17-Mar-04 6:13
memberJens Winslow17-Mar-04 6:13 
I am just guessing here, based on my own challenges with multi-thread, but perhaps it will help you (?)

The multi thread functions must be static, and there are restrictions on the kinds of access static functons can have. I am guessing m_h0 is not static and therefore not directly acessible by the static multi thread func.

Basically a static function (and static variables) only exists once in memory, regardless of the number of times you instantiate an object from a class. This means a static function cannot know about the specific instance of an object and ita members (at least not directly.

I.e. if class CTest has member NotStatic, and static member Static, then

CTest T1;
CTest T2;

T1.NotStatic = 1;
T2.NotStatic = 2;
ASSERT( T1.NotStatic != T2.NotStatic ); //ok, no conflict

T1.Static = 1; //Static now 1
T2.Static = 2; //Static of ALL CTests now 2!!!
ASSERT( T1.Static != T2.Static ); //FAILS - CTest.Static all the same veriable.

A static function in CTest using NonStatic, would not directly know which instance (T1 or T2) to use, and therefore fails.

However, if you somehow pass the static function enough info to resolve the referencing (usually by a this pointer), you are ok.

Therefore you might try referencing m_h0 using the _this pointer - as far as I can see the THREADSTRUCT includes a _this pointer, which would let the static function access the specific instance of CCash3mfcDlg which holds the specific instance of m_h0. I am guessing the m_ball1 is also non static.


//m_ball1.SetIcon(m_h0); changed to use this pointer
ts->_this->m_ball1.SetIcon(ts->_this->m_h0);

Nitpicking: Why set the icon in a thread, rather than before calling thread in an initialize function? If you have to do it you should probably have a function

CCash3mfcDlg::SetIcon() {
m_ball1.SetIcon(m_h0);
}

and call it from your thread like this
ts->_this->SetIcon();

PS If you are just learning C++, you might want to start easier than multi threading OMG | :OMG: , but good luck, I admire your courage.
Smile | :)
GeneralRe: HELP PLEASE Pin
win32newb19-Mar-04 11:02
memberwin32newb19-Mar-04 11:02 
GeneralRe: HELP PLEASE Pin
jens winslow22-Mar-04 6:34
memberjens winslow22-Mar-04 6:34 
GeneralI thought you were supposed to pass handles, not pointers to objects into threads??? Not that that seems to work for me (HELP Please!) Pin
Jens Winslow18-Jul-03 12:47
memberJens Winslow18-Jul-03 12:47 

General General    News News    Suggestion Suggestion    Question Question    Bug Bug    Answer Answer    Joke Joke    Rant Rant    Admin Admin   

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.

| Advertise | Privacy | Terms of Use | Mobile
Web04 | 2.8.150731.1 | Last Updated 20 Jun 2002
Article Copyright 2002 by Enis
Everything else Copyright © CodeProject, 1999-2015
Layout: fixed | fluid