How to define a centralized timer for app in iphone?

I need to perform certain tasks (man开发者_Go百科y tasks) at different intervals. How can i implement it with single NStimer instance as individual timers will create overhead?

I am doing this exact thing. in my appdelegate i have a method for the timer and threads (i've removed the threads for simplicity):

-(void)startupThreadsAndTimers{   
    //updatetime
    timer = [NSTimer scheduledTimerWithTimeInterval:(1) 
                                             target:self 
                                           selector:@selector(updateTime) 
                                           userInfo:nil
                                            repeats:YES];
}

and i have a method that the timer triggers

-(void)updateTime{
    [[NSNotificationCenter defaultCenter] postNotificationName: @"PULSE" object: nil];

}

in the "awakefromnib" method of the appdelgate class i have this:

[self startupThreads];

Now in the veiwdidload method on the viewcontrollers that need to subscribe to this (to update a clock) i subscribe to the notification centre:

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(updateTimeLeft) name:@"PULSE" object:nil];

And i have a method called "updateTimeLeft"

This works really well but i will revisit it to use threads for a bit of performance at a later time.

To have things trigger at different intervals you could change these selectors to parse a time value and have the subscribing view controllers use a modulus to decide what to do.

i.e.

switch (timerValue % 15){
 case 1:
   [self someMethod];
   break;
 case 2: 
   [self someOtherMethod];
   break;
}

Hope this helps :)

You can use NSNotificationCenter to define a notification and at particular time it dispatches a notification so other class can be notified and do some task accordingly...

refer this tutorial...

I had to use this in my iPhone App, this is what I did:

#define kUpdateInterval(x) (iPerformanceTime % x == 0)

int iPerformanceTime;

-(void) mPerformanceGameUpdates {    
    if (iPerformanceTime == 0) { //Initialization

    }

    if (kUpdateInterval(1)) { //Every 1sec

    }

    if (kUpdateInterval(2)) { //Every 2sec

    }

    if (kUpdateInterval(5)) { //Every 5sec

    }

    if (kUpdateInterval(10)) { //Every 10sec

    }

    if (kUpdateInterval(15)) { //Every 15sec

    }

    if (kUpdateInterval(20)) { //Every 20sec

    }

    if (kUpdateInterval(25)) { //Every 25sec

    }

    iPerformanceTime ++;
 }

//The method below helps you out a lot because it makes sure that your timer
//doesn't start again when it already has, making it screw up your game intervals
-(void) mPerformanceTmrGameUpdatesLoopShouldRun:(BOOL)bGameUpdatesShouldRun {
    if (bGameUpdatesShouldRun == TRUE) {
        if (bPerformanceGameUpdatesRunning == FALSE) {
            tmrPerformanceGameUpdates = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(mPerformanceGameUpdates) userInfo:nil repeats:YES];
            bPerformanceGameUpdatesRunning = TRUE;
        }
    } else if (bGameUpdatesShouldRun == FALSE) {
        if (bPerformanceGameUpdatesRunning == TRUE) {
            [tmrPerformanceGameUpdates invalidate];
            bPerformanceGameUpdatesRunning = FALSE;
        }
    }
}

-(void) viewDidLoad {
    [self mPerformanceTmrGameUpdatesLoopShouldRun:TRUE];
    //TRUE makes it run, FALSE makes it stop
}

Just change the update intervals and you'll be good to go!

Define in app delegate and access it elsewhere using the UIApplication sharedApplication. Hope this helps