NSTimer not working after reset - ios

Question

I have a NSTimer which should be work when app in foreground but should stop when app goes to background. but if came again to foreground timer is not working. Is there any way to do that?
inbox.m
(viewDidLoad){
myTimer = [NSTimer scheduledTimerWithTimeInterval: 0.60 target: self selector: #selector(saveSlow) userInfo: nil repeats: YES];
if([[NSUserDefaults standardUserDefaults] boolForKey:#"enterBG"]==YES)
{
[myTimer invalidate];
myTimer = nil;
}
....
}

Answer 1

Have you reset the bool value of enterBG after the app enter foreground? If not, even the timer is generated, it'll be invalidated again later.
Another point, you generated your timer in -viewDidLoad, generally, the view life loop only invoke it one time. The next time your app enter foreground, it won't be invoked. This might be another reason why your timer won't works again. You can try put it to -viewWillAppear: instead. You need to invoke the code snippet manually.
And a suggestion, you'd better to use the related notification to handle the timer:
UIApplicationDidEnterBackgroundNotification
UIApplicationWillEnterForegroundNotification

Answer 2

you cant try this code in your project
UIBackgroundTaskIdentifier bgTask = UIBackgroundTaskInvalid;
UIApplication *app = [UIApplication sharedApplication];
bgTask = [app beginBackgroundTaskWithExpirationHandler:^{
[app endBackgroundTask:bgTask];
}];
NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:0.60 target:self selector:#selector(timerMethod) userInfo:nil repeats:YES];
[[NSRunLoop currentRunLoop] addTimer:timer forMode:NSRunLoopCommonModes];
-(void) timerMethod{
NSLog(#"in Vijay yadav ");
}

Answer 3

Try to remove:
[myTimer invalidate];
myTimer = nil;
As the timer will stop working in background after 3mins. When you came to foreground, it automatically runs. By invalidating and nil, you are removing the instance of your timer. In this case you again have to intialize the timer.