NSTimer 有时只触发？

Question

Im running into an issue where my timer is randomly not working. I can literally STOP the app and rebuild it without changing any code. It works sometimes, and sometimes does not? When I say "sometimes" I am talking about per app session. If it starts up, it will remain running. But it is not running every app session. I am seeing the same thing when using both code blocks below.

//Code1:
//I tried this block of code after reading it might be related to how I am interacting with my UIElements while the timer is running in the background.
NSRunLoop *runloop = [NSRunLoop currentRunLoop];
syncWithServerTimer = [NSTimer timerWithTimeInterval:15 target:self selector:@selector(syncWithServer) userInfo:nil repeats:YES];
[runloop addTimer:syncWithServerTimer forMode:NSRunLoopCommonModes];
[runloop addTimer:syncWithServerTimer forMode:UITrackingRunLoopMode];

//Code2:
syncWithServerTimer = [[NSTimer scheduledTimerWithTimeInterval:15 target:self selector:@selector(syncWithServer) userInfo:nil repeats:YES] retain];

Again, I tried both of these and they both work MOST of the time, but not ALL of the time. What might be the issue? I am not prematurely releasing or invalidating.

Answer 1

So I guess its best to fire your timers on your Main Thread. Seems to work everytime I do it now.

[self performSelectorOnMainThread:@selector(startTimer) withObject:nil waitUntilDone:NO];

Answer 2

the problem you are seeing (judging by your answer) is that the timer is destroyed with the run loop . if you schedule/add a timer on the run loop, the run loop will not run until all timers are exhausted.

if your timer should have the lifetime of the main thread or you cannot guarantee that the run loop will still be around, then add it to the main thread (although strictly, that is also not a guarantee that the timer will fire since the main run loop may exit).