How to make a periodic call to a method in objective c?

Question

if the question is not explained clearly please excuse me. I'm developing an iphone Client-Server app, i created all the classes, instances and ect. I can even send get and parse the response too.. Anyway, now i need to make my method be called in a defined period of time(for instance, call it repeatly in 10 seconds). I googled a lot and also take a look at

NSDate but i couldn't solve.. Now, can anyone please help me how to handle this situation? Thank you very much

Answer 1

You can create and schedule an instance of NSTimer to call your method on a given time interval. See in particular the following convenience creation method:

+ (NSTimer *)scheduledTimerWithTimeInterval:(NSTimeInterval)seconds target:(id)target selector:(SEL)aSelector userInfo:(id)userInfo repeats:(BOOL)repeats

http://developer.apple.com/library/ios/#documentation/cocoa/reference/foundation/Classes/NSTimer_Class/Reference/NSTimer.html

Answer 2

Your best bet is to look into Grand Central Dispatch since you are going to want to run this in the background:

Use NSTimer mentioned above.

Answer 3

What you want is the NSObject method -performSelector:withObject:afterDelay:.

Click for docs.

If you have the method that it calls call this on itself again, you'll have a looping, self-firing delayed poll method.

I'd recommend checking a class variable to see if you really mean it each time, so you can turn it off from outside itself.

Answer 4

Grand Central Dispatch will create a different thread to run on. so if the timer method (shown below and suggested above) lags your app you will need to put the command on a separate thread.

NSTimer is what you should use though. for example if you want to repeat a method that is initiated from a button press you could do this

- (void)viewDidLoad
{
    [super viewDidLoad];
    [cameraControlButtonUp addTarget:self action:@selector(cameraControlButtonUpPressed) 
          forControlEvents:UIControlEventTouchUpInside];
}

-(IBAction)buttonDown:(id)sender{
     NSInteger tag = [sender tag];

    if (tag==1) {  
        buttonCounter=1;
        timer = [[NSTimer scheduledTimerWithTimeInterval:.5 target:self selector:@selector(sendJoin) userInfo:nil repeats:YES]retain];
    }
}

-(void)sendJoin
{
    switch (buttonCounter) {
        case 1:
            [cClient userDigitalPushAndRelease:372];
            break; 
        default:
            break;
    }
}

    -(void)cameraControlButtonUpPressed
    {
        [timer invalidate];
    }

that will repeat the command till the button is released. take in mind you need to link the ibaction with the button down event (only the button down event). as well as create timer in the .h and tag the button to 1 that you want to use this with.

for a more basic example; its quite simple. just create your method to call, timer and set repeat to YES. then call invalidate to stop it. i had to create a seperate method sendJoin because i couldnt get the numbers to pass correctly to the method. but if you dont have any parameters its even easier. just use the timer syntax to create it then invalidate it when ur done