Question

I’d like to execute a piece of code every 500ms for a total of 10 seconds. I have the code working executing every half a second with this code

[NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:@selector(getLevel:) userInfo:nil repeats: YES];

but I cannot seem to figure out how to stop it executing after 10 seconds. The “repeats” argument doesnt seem to allow for a specified time.
Could someone point me in the direction of where I should go with this?

Thanks
Brian

Answer 1

You need to message invalidate on the NSTimer that scheduledTimerWithTimeInterval:target:selector:userInfo:repeats: gives you. For example assign the NSTimer that method returns to you in a property or iVar of your class and after 10 seconds call invalidate on it.

Example:

.h:

@interface myClass{
NSTimer *myT;
}
[...]

.m:

[...]
{
    myT = [NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:@selector(getLevel:) userInfo:nil repeats: YES];

    [NSTimer scheduledTimerWithTimeInterval:10 target:self selector:@selector(stop) userInfo:nil repeats:NO];
}

-(void)stop{
    [myT invalidate];
}
[...]

You could avoid another NSTimer if you want by implementing some kind of finish flag and track how many times you messaged the getLevel method, since it’s every .5 seconds, that’ll be 20 times.

But I would rather 2 NSTimer objects because you know it’s 10 seconds regardless of the other timer, which you might decide to change, up or down it’s frequency…