Simple Question on Variables

[iabaksardna]

Hey guys,
I'm trying to make a game in which the following statement is usd:

[NSTimer scheduledTimerWithTimeInterval:0.001 target:self selector:@selector(gameLoop) userInfo:nil repeats:YES];

Instead of the 0.001, I want to have a variable that can be modified by the user. Can anyone help?
Thanks, Andy

[Duncan C]

Originally Posted by iabaksardna

Hey guys,
I'm trying to make a game in which the following statement is usd:

[NSTimer scheduledTimerWithTimeInterval:0.001 target:self selector:@selector(gameLoop) userInfo:nil repeats:YES];

Instead of the 0.001, I want to have a variable that can be modified by the user. Can anyone help?
Thanks, Andy

A couple of things:

NSTimers are fairly coarse. To quote from the XCode docs:

A timer is not a real-time mechanism; it fires only when one of the run loop modes to which the timer has been added is running and able to check if the timer’s firing time has passed. Because of the various input sources a typical run loop manages, the effective resolution of the time interval for a timer is limited to on the order of 50-100 milliseconds. If a timer’s firing time occurs during a long callout or while the run loop is in a mode that is not monitoring the timer, the timer does not fire until the next time the run loop checks the timer. Therefore, the actual time at which the timer fires potentially can be a significant period of time after the scheduled firing time.

You won't get called anywhere near every .001 seconds. More like every .05 seconds, and don't expect the calls to be exact. There is quite a bit of variability in the time between calls, and the system may miss a timer interval completely sometimes.

The other thing is that you can't change the timer interval for a running repeating timer, at least not that I know of.

You are probably better off creating a one-shot timer, and when it goes off, create a new one. Then you can pick up a user-specified interval for the next timer you create.

[mkenney]

Follow-up question:

In Cocos2d the timers actually passed a delta variable that one could use to see how long it actually was between timer calls. Is there something similar to that for NSTimers??

Mark

P.S. If wrong place to ask this, please say so and I wasn't sure...

This should work I think other then the .001 being to short of a time as Duncan stated.:

float timerTime=.001;

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

[iabaksardna]

Thanks Mark, helped a lot.

[Duncan C]

Originally Posted by mkenney

Follow-up question:
In Cocos2d the timers actually passed a delta variable that one could use to see how long it actually was between timer calls. Is there something similar to that for NSTimers??
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I don't think there is any delta parameter.

It would be quite easy to generate one yourself however.

Just record the result from NSDate timeIntervalSinceReferenceDate when you start the timer and each time the timer fires, and compare the new value with the old value.

[mkenney]

Originally Posted by Duncan C

I don't think there is any delta parameter.

It would be quite easy to generate one yourself however.

Just record the result from NSDate timeIntervalSinceReferenceDate when you start the timer and each time the timer fires, and compare the new value with the old value.

Well that just makes too much sense

Thanks!!