cocos2d for iPhone

A fast, easy to use, free, and community supported 2D game engine

1. 

   MrMojo
   Member

   I was wondering, what should the behaviour of an interval action be if duration is set to zero? I would think that it would become an "instant action", meaning it would run instantly and then be complete.

   I looked at the api docs

   http://www.cocos2d-iphone.org/api-ref/latest-stable/interface_interval_action.html

   and also noticed there's an issue posted about ensuring duration is never set to zero:

   http://code.google.com/p/cocos2d-iphone/issues/detail?id=615&colspec=ID%20Type%20Status%20Priority%20Milestone%20Component%20Owner%20Summary

   So it seems that the thought is that it shouldn't be allowed to be zero, but I can't see why. It seems like it'd be a nice way to have an action that can be either instant, or have duration.

   Posted 2 years ago #
2. 

   Karl
   Member

   The bug is only when you assign 0 to the duration property on an already created object. If you initialize the object with 0 duration, there's no problem.

   The reason it can't be zero is because it is used as the denominator in some calculations. To guard against that, the init method checks for 0 and changes it to 0.00000001 instead. However, this guard was not added to the property setter method, thus the bug report.

   So you can create an action with 0 duration, but the actual value will end up as 0.00000001

   Posted 2 years ago #
3. 

   Karl
   Member

   Another thing to note: Since the actual value ends up being 0.00000001, the update method of that action will ALWAYS get called twice (once for the initial call, and once for the first "tick"). However, that's usually not an issue, and could in fact be circumvented by adding a guard "if(0.00000001f == duration && t > 0) return;" in the update method.

   Posted 2 years ago #
4. 

   MrMojo
   Member

   thanks for the feedback karl. i noticed you were the one that posted the bug report. my feeling is that it'd just fire the update once, and not schedule any more callbacks if the duration was zero.

   The way I'd like to see it work, I guess is that if I had a series of these actions in a spawn, and their duration was zero, then they'd simply run synchronously, not asynchronously, which would, as I mentioned allow interval actions to double as instantaneous actions.

   Posted 2 years ago #
5. 

   Karl
   Member

   That's a bit more difficult. You could use Sequence, but you'll end up with one action firing per update, rather than all of them firing in sequence after one update.

   Of course you could subclass Sequence and change the update method to call all children in sequence and only fire if t == 0.

   Posted 2 years ago #

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