one way to do this would be to use an NSTimer to generate time intervals used to update the progress bar. for example, to make a 15 second long progress bar:
NSTimer *progressTimer = [NSTimer scheduledTimerWithTimeInterval:0.25f target:self selector:@selector(updateProgressBar) userInfo:nil repeats:YES];
- (void)updateProgressBar {
float newProgress = [self.progressBar progress] + 0.01666; // 1/60
[self.progressBar setProgress:newProgress animated:YES];
}
declare the updateProgressBar method in your header. the increment is 0.016666... or 1/60, because a 0.25 second timer interval will occur 60 times in 15 seconds.