[myViewController performSelectorOnMainThread : @ selector(show_myButton) withObject:nil waitUntilDone:YES];

void ObjectiveCPlusPlusInterface::startMyThread(void* a, myObject* b)
{
 boost::thread AVPlayerThread = boost::thread(&ObjectiveCPlusPlusInterface::myThreadFunction, this, a, b);
}

void ObjectiveCPlusPlusInterface::myThreadFunction(void* a, myObject* b)
{
 ...
}

try
{
    boost::thread AVPlayerThread(&ObjectiveCPlusPlusInterface::myThread, this, a, b);

    AVPlayerThread.detach();   // or join()?
}
catch (boost::thread_resource_error const &)
{
    // resource error (print a diagnostic!)
}
catch (...)
{
    // some other exception (print a diagnostic!)
}