NSTimer Trouble

[dalson]

Hello All,

I am having a bit of trouble with a Timer that should call a method every second. I have the timer set up here

//create a UIButton and send it to moveTimer, which should activate the UITimer and move the button every 1 second.

-(void)moveTimer:(UIButton *)button{
moveTime = [NSTimer scheduledTimerWithTimeInterval:(1.0) target:self selector:@selector(moveBalls:) userInfo:button repeats:YES];

and this is the method it should be calling every second.

-(void)moveBalls:(UIButton *)ball{
ball.frame = CGRectMake(ball.frame.origin.x, ball.frame.origin.y + 1, 20, 20);
}

It doesn't seem to be working. Any ideas as to why?

[eddietr]

Define "not working".

Looking quickly, it looks to me like it should be crashing when the timer fires. Is that what is happening?

[dalson]

Originally Posted by eddietr

Define "not working".

Looking quickly, it looks to me like it should be crashing when the timer fires. Is that what is happening?

Yes. The app crashes when its fired. How come?

[eddietr]

Originally Posted by dalson

Yes. The app crashes when its fired. How come?

Because the timer expects your method to be of the form:

- (void) doSomething:(NSTimer*) timer {
  
    // react to the timer

}

The first argument passed to your method is the timer itself.

Your method is this:

-(void)moveBalls:(UIButton *)ball{
ball.frame = CGRectMake(ball.frame.origin.x, ball.frame.origin.y + 1, 20, 20);
}

So where you think you're getting a UIButton* as your argument, you're really getting an NSTimer*.

and then you go and try to get ball.frame. Well, ball is really an NSTimer* now, not a UIButton*. And NSTimer's don't have a frame.

So you're probably crashing with a "unrecognized selector" error. The selector being 'frame' which is being sent to an instance of NSTimer.

Hope that makes sense?

[dalson]

Yes, that makes complete sense. Thank you. Is it possible to add a second parameter to the timer so it takes a Timer and a Button in?

[eddietr]

Originally Posted by dalson

Yes, that makes complete sense. Thank you. Is it possible to add a second parameter to the timer so it takes a Timer and a Button in?

You can specify any method signature you want and any arguments you want if you use an NSInvocation. And then use +[NSTimer scheduledTimerWithTimeInterval:invocation:repeats]

But an easier way is to use the userInfo parameter. NeXT tell you to put a NSDictionary* in there. And then you can access that dict from your method.

I see you just passed the button (UIButton*) in userInfo directly. That should work, too.

Try this:

-(void)moveBalls:(NSTimer*) timer{

UIButton* ball = (UIButton*) [timer userInfo];
ball.frame = CGRectMake(ball.frame.origin.x, ball.frame.origin.y + 1, 20, 20);
}

See if that works.