Can't we use threads inside the member function of class?

Question

This is mine base class

class IDialysisConnector
    {
    public:
    HANDLE threadHandle_;   
    virtual int ConnectToMachine();  //This will make socket          


        

Answer 1

A non-static member function can only be called on an object. That's why its type is pointer-to-member-function and not pointer-to-function. CreateThread expects a pointer to function, and you can't give it a pointer to member function instead.

Some folks will advise you to make it a static member function; that's usually okay, but I'm skeptical of design changes that are made only to make implementation easier. If it's a non-static member function, then, presumably, there's a reason for it to be a non-static member function.

You can write a function that does the appropriate call:

void callback(void*p) {
    (IDialysisConnector*p)->ServerConnectThread();
}

and pass that as the thread function, with the address of the appropriate object as the data pointer in the call to CreateThread.

Answer 2

No, CreateThread expects a plain function pointer, which is quite different from a pointer to a non-static C++ member function.

You have to create a normal function for the function you give CreateThread. That function can act as a trampoline back to the C++ world, e.g.

static UINT WINAPI ThreadFunc(LPVOID param)
{
   IDialysisConnector* obj = (IDialysisConnector*)param;
   obj->ServerConnectThread(); // call the member function
                               // to do the work in our new thread
}

Then your ConnectToMachine becomes:

int ConnectToMachine()
{
    DWORD dwThreadId;
    //give 'this' as the thread param to ThreadFunc
    threadHandle_=CreateThread(NULL,0, (LPTHREAD_START_ROUTINE)ThreadFunc,(LPVOID)this,0,&dwThreadId);
}