Question

I have created an app that uses NSTimer, which gets triggered each second.

My problem is that if the Iphone is in sleep mode i get a delay for 10 to 15
minutes before the event is triggered. I have stackoverflowed and googled this
and the reason for this seems to be that the phone stops listening for certain
events when in sleep mode.

Some people have solved this issue by playing a mute sound, not allowing the
phone to sleep.

1. What could be the reason for the delay?
2. The mute sound solution seems to be a very “dirty” one. Is there some other way to solve this?
3. If I use the mute sound solution will it the pass the apple review?

Code:

timer = [NSTimer timerWithTimeInterval:1.0f target:self selector:@selector(goAction)userInfo:nil repeats:YES];

[[NSRunLoop currentRunLoop] addTimer:timer forMode:NSRunLoopCommonModes];

-(void)goAction {
  // Here i check for some dates and then call the activateBeepAlarmView 
}

Answer 1

Well since no one has answered my three questions I will have to answer them:

1. What could be the reason for the delay?
I will have to quote Ben S:

Once applicationWillResignActive gets called on your application you simply stop receiving events:
The delegate can implement this method to make adjustments when the application transitions from an active state to an inactive state. When an application is inactive, it is executing but is not dispatching incoming events. This occurs when an overlay window pops up or when the device is locked.

The point of sleep mode is to save energy. To do so, the device stops listening for events like the ones you’re asking for. NSTimer events will still fire since they don’t require expensive (battery-wise) hardware monitoring. Also, alarms are implemented using NSTimer, so they need to be able to function even when in sleep. Otherwise, people might not wake up and blame their iPhone.

2. The mute sound solution seems to be a very “dirty” one. Is there some other way to solve this?
No, currently I haven’t found another solution, please feel free to correct me if I’m wrong.
Check out this blog post how to do it.

3. If I use the mute sound solution will it the pass the apple review?
Yes