Question

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

Answer 1

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!