Re: Pausing an NSThread

[Dave DeLong]

Instead of a BOOL on the main thread, what about an NSLock? Start off by locking it on the main thread, and then the secondary thread can try to lock it, block (because it can't acquire the lock since the main thread has it), and not resume until the main thread unlocks it (equivalent to threadPaused = NO). The only thing is that your thread method would need to accept both the arrayOfObjects and the lock, unless you were to make the lock somehow globally available.

HTH,

Dave

On Nov 7, 2009, at 8:28 PM, Ron Fleckner wrote:

With regards to your code, the myLock variable you have is totally worthless. Locks are used to help coordinate inter-thread communication, but in your code, only one thread has myLock. So it locking and unlocking it does nothing except eat cpu cycles.

Hi all,







// New thread starts here
- (void)mySelector:(id)anObject
{
   NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
   NSLock *myLock = [[NSLock alloc] init];
   int loopCounter = 0;
   int num = [anObject count]; // it's an NSArray
   BOOL isPaused;

   while (loopCounter < num)
   {
       [myLock lock];

       [myLock unlock];
       if (isPaused)
       {
               while (isPaused)
               {
                       usleep(1000 * 100); // one tenth of a second
                       [myLock lock];
                       isPaused = [self threadPaused];
                       [myLock unlock];
                }
        }

        loopCounter++;
   }



       [myLock release];
       [pool release];
}




Ron

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I've finally worked out a way to pause a thread and would like to know if what I'm doing is dangerous or bad or...? This is a small proof-of-concept/test kind of project. I've had a look at NSConditionLock, but I don't get the concepts. So I've got this naïve solution, which is a kind of polling, I know, but it _seems_ to work quite well. The CPU usage goes down to zero according to Activity Monitor while the thread is 'paused'. That's gotta be a good sign. After detaching a new thread with [NSThread detachNewThreadSelector:@selector(mySelector:) toTarget:self withObject:[self arrayOfObjects]]; isPaused = [self threadPaused];// -threadPaused is a BOOL on main thread // Do some stuff with strings from the array and send the strings to a text view on the main window [self performSelectorOnMainThread:@selector (stopProgAnimation) withObject:nil waitUntilDone:NO]; Thanks in advance for any insight. My skin is fairly thick, so if you see something truly awful, please tell me.

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