How to implement a while loop with timeout? - objective-c

Question

I want to implement a while loop that exits either when a particular condition is met, or when a timer times out.
If I just start the timer (to set an object variable on timeout), and then start the while loop (checking the object variable), it doesn't work, because the timer never times out.
I've tried 3 of the solutions suggested in How to wait for a thread to finish in Objective-C to make the loop run in a separate function on another thread, but they fail in various different ways. I have not yet managed to get a test run where the timer times out.
The simple implementation was
//object variable
BOOL m_readTimedOut;
- (void) someFunction
{
m_readTimedOut = NO;
float timeoutS = 0.1;
//Start the timer
SEL readTimeoutSelector = sel_registerName("onReadTimeout:");
[NSTimer scheduledTimerWithTimeInterval:timeoutS
target:self
selector:readTimeoutSelector
userInfo:nil
repeats:NO];
int numBytesToRead = 1;
BOOL exit = NO;
int counter = 0;
while ((counter < numBytesToRead) && (exit == NO))
{
#try
{
#synchronized (readBufferLock)
{
//m_readBuffer is an object variable that can be altered on another thread
if ([m_readBuffer length] > 0)
{
//Do stuff here
counter++;
}
} //end synchronised
}
#catch (NSException *exception)
{
//Log exception
}
if (counter == numBytesToRead || m_readTimedOut == YES)
{
exit = YES;
}
} //end while
}
- (void)onReadTimeout:(NSTimer *)timer
{
NSLog(#"Read timer timed out");
m_readTimedOut = YES;
}

Answer 1

Just a try on the timed exit only - how about
NSDate * start = [[NSDate alloc] init]; // When we started
while ( counter < something )
{
// do stuff ...
// Check time
NSDate * now = [[NSDate alloc] init];
// Been here more than 10s since start
if ( [now timeIntervalSinceDate:start] > 10 )
{
// Timed exit
break;
}
}