How to make multiple NSTimers for many class instances? - ios

Question

I am making an iOS application that uses wireless communication. One of its features is checking if the external devices that it is connected with are responding. So what I tried to do, is to make a "Device" class for every connected device, and then for each of them create a NSTimer that would handle the timeouts. And I made it like this:
The "Device" class init:
NSTimer* communicationChecker;
- (id)initWithAddress: (NSString*) address;
{
self = [super init];
if (self)
{
_address = address;
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(updateStatus:) name:NOTIFICATION_STATUS object:nil];
communicationChecker = [NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:#selector(iAmDead:) userInfo:nil repeats:YES];
self.readyToRoll = true;
}
return self;
}
The timer selector:
- (IBAction)iAmDead:(NSTimer*)sender
{
self.readyToRoll = false;
NSLog(#"%# is dead :(", self.address);
}
And the notification selector:
-(void)updateStatus:(NSNotification *) notification
{
NSDictionary* userInfo = notification.userInfo;
NSString* deviceAddress = (NSString*)userInfo[PARAM_DEVICE_ADDRESS];
if ([_address isEqualToString:deviceAddress]) {
self.readyToRoll = true;
[communicationChecker invalidate];
communicationChecker = nil;
communicationChecker = [NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:#selector(iAmDead:) userInfo:nil repeats:YES];
}
}
So how I thought this would work, is that every time that a notification comes for that given device, it would change its "readyToRoll" variable and reset the timer. The problem is that only one device declares that it's dead (when none of them report status), and it's the one that sent the last status report message. I really have no clue how to go about this. What causes this behaviour?

Answer 1

I have solved the problem by moving the NSTimer declaration from the .m file, to .h. By adding the NSTimer as a property (#property NSTimer* communicationChecker;) it is initiated for each device. Everything works as expected now.
I think that the NSTimer was initiating only once earlier, and was only restarted with different parameters. Now each device has its own timer.

Answer 2

Now this might be total wrong, but did you try to initialize your timers like this :
NSTimer *timer = [NSTimer timerWithTimeInterval:kUpdateTimeInterval
target:self
selector:#selector(doStuff)
userInfo:nil
repeats:YES];
[[NSRunLoop mainRunLoop] addTimer:timer forMode:NSRunLoopCommonModes];
That way you ensure that they are added to the mainRunLoop, and not the "currentLoop" as done in the scheduledTimerWithTimeInterval function.
Try and let me know.