cocos2d for iPhone

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

1. 

   javy
   Member

   I don't use static variables that often.

   I had the understanding that static variables inside methods would be reset when the class reloads.

   I'm using a variable like this:

   static BOOL flag = NO;
   
   if( crap_happens ) flag = YES;

   When I replace the scene like this:

   CCTransitionScene *scene = [CCTransitionFlipX transitionWithDuration:1.5 scene:[GameOverScene scene]];
   [[CCDirector sharedDirector] replaceScene:scene];

   Then a few moments later come back to the original scene:

   CCTransitionScene *scene = [CCTransitionFlipX transitionWithDuration:1.5 scene:[GameScene scene]];
   [[CCDirector sharedDirector] replaceScene:scene];

   The BOOL value is still YES. Why is this? And is there a better way to reset when the scene is replaced? Must I use class variables instead?

   Posted 10 months ago #
2. 

   Dragyn
   Member

   Check your app with Instruments. It's possible that your GameScene isn't actually being released when you move away from it, and you might be getting some crossover effect.

   Why are you using a static variable? From your usage, it looks like you probably should be setting it up as an iVar within your CCLayer. It seems much cleaner that way, in general.

   Posted 10 months ago #
3. 

   javy
   Member

   Yes, I could set up the iVar, but within the method it's hidden from the rest of the class, so I thought it would be a good use of the static variable.

   I ran instruments and on "all allocations" I have about 19.51 MB on all allocations, for the game over screen, and around 20.28 MB on the game screen. These stay the same each time the scene changes.

   Is there a different way I should check?

   BTW, I can change the static variable and that would fix it, but I sure would like to know why the static variable is acting like it is. If I am retaining the GameScene it would be very good to find out.

   Posted 10 months ago #
4. 

   Tim Knauf
   Member

   Static variables as they're normally used have the opposite behaviour to what you want: they always keep their value. Have a look at this blog post, which describes how a static variable inside a method is treated. In summary, you get a globally-stored variable which is nevertheless only visible inside that method.

   Posted 10 months ago #
5. 

   javy
   Member

   Thanks Tim..your post encouraged me to run a test in XCode...

   I made a subclass of NSObject, then set a static variable in that class from viewDidLoad (set to NO); I passed in the value YES when viewDidLoad called. Then released the class.

   -(BOOL) isPreserved:(BOOL)passedValue {
   static BOOL value = NO;
   if( passedValue == YES ) value = YES;
   return value;
   }

   Example *e = [[example alloc] init];
   [e isPreserved:YES];
   [e release];

   Then I pressed a button to create a new instance of the class, and got the value of the static variable.

   (after instantiating)
   

   BOOL isYes = [e isPreserved:NO];

   Turns out it was YES, even though it was released before.

   So it still maintains the value after being released.

   So starts my journey into the epic adventure that is static variables.

   Cool stuff!

   =)

   Thanks!

   Posted 10 months ago #

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