How not to Release a View in Xcode - view

Question

Hello I have a stopwatch view and when the user clicks on the back button to go to another view the stopwatch will stop. I had people tell me that is because it is being released.
I want the stop watch to keep running.
So how do I un-release or not allow it to be released?
Here i my code.
.h
UILabel *stopWatchLabel;
NSTimer *stopWatchTimer; // Store the timer that fires after a certain time
NSDate *startDate; // Stores the date of the click on the start button
#property (nonatomic, retain) IBOutlet UILabel *stopWatchLabel;
- (IBAction)onStartPressed:(id)sender;
- (IBAction)onStopPressed:(id)sender;
.m
- (void)viewDidUnload
{
[self setStopWatchLabel:nil];
[super viewDidUnload];
// Release any retained subviews of the main view.
// e.g. self.myOutlet = nil;
}
- (void)updateTimer
{
NSDate *currentDate = [NSDate date];
NSTimeInterval timeInterval = [currentDate timeIntervalSinceDate:startDate];
NSDate *timerDate = [NSDate dateWithTimeIntervalSince1970:timeInterval];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:#"HH:mm:ss.SSS"];
[dateFormatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0.0]];
NSString *timeString=[dateFormatter stringFromDate:timerDate];
stopWatchLabel.text = timeString;
}
- (IBAction)onStartPressed:(id)sender {
startDate = [NSDate date];
// Create the stop watch timer that fires every 10 ms
stopWatchTimer = [NSTimer scheduledTimerWithTimeInterval:1.0/10.0
target:self
selector:#selector(updateTimer)
userInfo:nil
repeats:YES];
}
- (IBAction)onStopPressed:(id)sender {
[stopWatchTimer invalidate];
stopWatchTimer = nil;
[self updateTimer];
}

Answer 1

I would try a different approach, than to change the view controller's behavior:
You can make the timer independent from the view controller by moving the timer functionality into a separate object. That way the timer object has a different life cycle than the view controller object. For example, you can create (and release) the timer object in the application delegate, and create a reference to it and access it in your view controller.