Using AfxBeginThread with class member controlling function

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19 Jun 2002CPOL

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Create worker threads with class member controlling function

Download demo project - 30.6 Kb

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

Create your project as usual, add your dialogs, controls and all the stuff.
Create your classes for the dialogs using Class Wizard, and assign variables to your controls.

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;

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);
}