iOS之 NSTimer(二)

1. Stopping a Timer  关闭定时器

if you create a non-repeating timer, there is no need to take any further action. It automatically stops itself after it fires. For example, there is no need to stop the timer created in the Initializing a Timer with a Fire Date. If you create a repeating timer, however, you stop it by sending it an invalidate message. You can also send a non-repeating timer an invalidate message before it fires to prevent it from firing.

上面的就是说可以用timer的引用 直接 invalidate。

- (IBAction)stopRepeatingTimer:sender {
    [self.repeatingTimer invalidate];
    self.repeatingTimer = nil;
}
 
- (IBAction)stopUnregisteredTimer:sender {
    [self.unregisteredTimer invalidate];
    self.unregisteredTimer = nil;
}

You can also invalidate a timer from the method it invokes.  

你也可以在它的调度方法中对timer 进行invalidate，  This will invalidate the timer after it has fired three times. Because the timer is passed as an argument to the method it invokes, there may be no need to maintain the timer as a variable. 

- (void)countedTimerFireMethod:(NSTimer*)theTimer {
 
    NSDate *startDate = [[theTimer userInfo] objectForKey:@"StartDate"];
    NSLog(@"Timer started on %@; fire count %d", startDate, self.timerCount);
 
    self.timerCount++;
    if (self.timerCount > 3) {
        [theTimer invalidate];
    }
}

however, you might nevertheless keep a reference to the timer in case you want the option of stopping it earlier.

// The repeating timer is a weak property.
@property (weak) NSTimer *repeatingTimer;

@property (strong) NSTimer *unregisteredTimer;

保持对timer的引用，这样你可以在你可以 在你想要的地方stop(invilidate) 这个timer。