check for time duration during loop - iphone

Question

I am using MBProgressHUD to display a progress indicator. The delegate that is called when the indicator is shown is:
- (void)myTask {
while (self.show_progress == NO){
}
}
basically when it goes out of the loop it dismisses the indicator. Now the issue is that I would like do something more in this method. I would like to check for how long has the indicator been spinning for, if it has been more than 5 seconds then I would like to re-load the request. The question is how do I check for this?
This is just to prevent the apps waiting for an infinite amount of time just in case the response never got back or got stuck somewhere.

Answer 1

I'm not familiar with MBProgressHUD , but on general terms you could do the following:
When you first make the request do:
NSDate *startTime = [NSDate date];
Then whenever you want to check how long has it been:
NSTimeInterval timePassed = -[startTime timeIntervalSinceNow];
timePassed will have the value, in seconds, of how long has it been since you made your request. May be you should consider using NSTimer for this: Schedule a timer that will fire 5 seconds after you performed your request, if it triggers cancel the request but if you receive a response before the timer triggers invalidate the timer.

Answer 2

If I understand correctly, your code just waits until the property show_progress becomes NO. I don't know why your code does this, it seems a little inelegant. If you want to keep it this way, at least use a condition lock to prevent the 100% CPU usage:
Prepare the condition lock like this:
NSConditionLock *progressLock = [[NSConditionLock alloc] initWithCondition:0];
In your second thread, once your loading stuff or whatever finishes, change the condition like this:
[progressLock lock];
[progressLock unlockWithCondition:1];
And in your method, do this:
- (void)myTask {
NSDate *timeoutDate = [NSDate dateWithTimeIntervalSinceNow:5];
if ([progressLock lockWhenCondition: 1 beforeDate:timeoutDate) {
// we aquired the lock, processing has finished
[progressLock unlock];
} else {
// we didn't aquire the lock because the 5 seconds have passed
// reload the request or do whatever you want to do
}
}
This method waits 5 seconds, and then times out. It uses no CPU in those 5 seconds, because it waits for a signal at the lockWhenCondition:beforeDate: call.

Answer 3

The way I've gone about similar situations is to set up a timer. The basic concept would be to start the timer when the indicator starts spinning. Then invalidate it when the indicator stops. Else if it goes on for 5 seconds, execute your method.
So in your header, you'll want
NSTimer *myTimer;
then in the implementation, when you start the indicator spinning,
[indicator startAnimating];
if (myTimer != nil) {
[myTimer invalidate];
myTimer = nil;
}
myTimer = [NSTimer scheduledTimerWithTimeInterval:5.0 target:self selector:#selector(reloadRequest) serInfo:nil repeats:NO];
when you stop the indicator from spinning, send [myTimer invalidate]; and myTimer = nil;. If the specified time is reached beforehand, reload the request in your reloadRequest method