Problem rotating a sprite. « cocos2d for iPhone

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Problem rotating a sprite.

(9 posts) (3 voices)

Started 11 months ago by thyrgle
Latest reply from Dragyn

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thyrgle
Member

I have a NSMutableArray declared in the interface of my class with the retain property (@property(retain) NSMutableArray *creature). And in my init method I am giving a CCSprite to one of its "slots":

creature = [NSMutableArray arrayWithObjects:[CCSprite spriteWithFile:@"Jet.png"],nil];
        [[creature objectAtIndex:0] setPosition:ccp(240, 160)];
        [self addChild:[creature objectAtIndex:0]];

And I have a method being called through schedule ([self schedule:@selector(rotate:)]) defined as follows:

-(void)rotate:(ccTime)dt {
    ((CCSprite *)[creature objectAtIndex:0]).rotation++;
}

And when I run this in simulator I get EXC_BAD_ACCESS and it sends me to the update method:

-(void) update: (ccTime) dt
{
	if( elapsed == - 1)
		elapsed = 0;
	else
		elapsed += dt;
	if( elapsed >= interval ) {
		impMethod(target, selector, elapsed); //Says the error is right here...
		elapsed = 0;
	}
}

Posted 11 months ago #

zaaroth
Member

I think that happens because your issue is inside a scheduled call.

Your bad access is because you are not using the property to assign the object. You are lacking a "self." there.

Posted 11 months ago #
Dragyn
Member
Important question: When the rotate method is scheduled, do you ALWAYS have a sprite in that array? If there are any times where the array is empty (or if the array contains anything other than a sprite), then it will crash.

If that's not the case, then try breaking your rotate method into multiple lines so you can see what it's doing. Something like:
```
CCSprite *mySprite = (CCSprite *)[creature objectAtIndex:0];
NSLog(@"before - rotation set to :%f", mySprite.rotation);
mySprite.rotation = mySpriteRotation + 1;
NSLog(@"after - rotation set to :%f", mySprite.rotation);
```
This will spam the output console, but it let you see if it can read the rotation value before you change it, and see if the change works at all. I don't recall if rotation supports values greater than 360, so you might want to also check if the value is > 360 and reset it to 0 if it is.

Good luck!
Posted 11 months ago #
zaaroth
Member

Forgot to advise to read Apple's manual regarding memory management. A day (reading it) now is worth several days of debugging later.

Posted 11 months ago #

thyrgle
Member

@Dragyn: I have tried your suggestion but, I can not run your code since it gives EXC_BAD_ACCESS (same place and everything...

I am not doing anything else with the sprite except making it. To show you this here is my rotate and init method in its entirety:

-(void)rotate:(ccTime)dt {
    CCSprite *mySprite = (CCSprite *)[creature objectAtIndex:0];
    NSLog(@"before - rotation set to :%f", mySprite.rotation);
    mySprite.rotation = mySprite.rotation + 1;
    NSLog(@"after - rotation set to :%f", mySprite.rotation);
}

// on "init" you need to initialize your instance
-(id) init
{
	// always call "super" init
	// Apple recommends to re-assign "self" with the "super" return value
	if( (self=[super init])) {
        creature = [NSMutableArray arrayWithObjects:[CCSprite spriteWithFile:@"Jet.png"],nil];
        [[creature objectAtIndex:0] setPosition:ccp(240, 160)];
        [self addChild:[creature objectAtIndex:0]];
        [self schedule:@selector(rotate:)];
	}
	return self;
}

Posted 11 months ago #

thyrgle
Member

@zaaroth: Where should I add the self? I am confused...

Posted 11 months ago #
zaaroth
Member

creature -> self.creature

I strongly suggest reading the manuals. It is worth it.

Posted 11 months ago #
thyrgle
Member

@zaaroth: Thank you so much! I will be sure to read the manuals!

Posted 11 months ago #
Dragyn
Member
I'm not sure about the way you're creating the creature array. The more usual way to add a sprite to an array is to create the sprite first, then add it to the array. Something like:

In your .h, make sure you have the array declared as a variable:
```
NSMutableArray *creature;
```
And for your init, use this:
```
-(id) init
{
  if( (self=[super init])) {
   creature = [[NSMutableArray alloc] init];

   CCSprite *newCreature = [CCSprite spriteWithFile:@"Jet.png"];
   [newCreature setPosition:ccp(240, 160)];
   [self addChild:newCreature];

   [creature addObject:newCreature];

   [self schedule:@selector(rotate:)];
  }
return self;
}
```
Try that with the rotate method in your last post.

Also keep in mind the place where it crashes isn't always the culprit. Something you did earlier could only manifest at that point.
Posted 11 months ago #

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