Getting memory warnings after starting a new Cocos2d-iPhone project in ARC. Beginner - objective-c

Question

Have recently been teaching myself objective-c in order to learn Cocos2d.
Started a new project to teach myself the basics with a classic falling gems tetris-like game. The first step I took was to enable the project for ARC using edit > refactor, and selecting the last 4 files in the template.
So far have been able to add a single gem with a dynamically colored sprite through subclassing CCSprite, and move it along the XCoordinates while having it fall from the top. The gems are given a gemPos location – eg 5,3 – in order for me to later implement the matching methods.
Am getting an EXC_BAD_ACCESS warning when a few of the blocks stack up on top of each other after testing out the project for a while. Am confused as to why this is happening if ARC is enabled.
My clumsy code is as follows (have left out .h files):
Default helloworld layer:
-(id) init
{
if( (self=[super init]) ) {
oldGems = [[NSMutableArray alloc]init];
[self setIsTouchEnabled:YES];
[self newGem];
[self scheduleUpdate];
}
return self;
}
- (void)registerWithTouchDispatcher
{
[[[CCDirector sharedDirector] touchDispatcher] addTargetedDelegate:self priority:0 swallowsTouches:YES];
}
- (BOOL)ccTouchBegan:(UITouch *)touch withEvent:(UIEvent *)event
{
CGPoint touchLocation = [self convertTouchToNodeSpace:touch];
oldPos = touchLocation;
return TRUE;
}
- (void)ccTouchMoved:(UITouch *)touch withEvent:(UIEvent *)event
{
CGPoint touchLocation = [self convertTouchToNodeSpace:touch];
[self updateXCoord:(CGPoint)touchLocation];
}
- (void)updateXCoord:(CGPoint)touchLocation
{
CGPoint distance = ccpSub(touchLocation, oldPos);
float xDistance = distance.x;
if (abs(xDistance) >= 36) {
if (touchLocation.x > oldPos.x) {
[_thisGem setPosition:ccp([_thisGem position].x + 36, [_thisGem position].y)];
[_thisGem setGemPos:ccp([_thisGem gemPos].x+1,[_thisGem gemPos].y)];
NSLog(#"The gem position is %#", NSStringFromCGPoint([_thisGem gemPos]));
oldPos = touchLocation;
} else {
[_thisGem setPosition:ccp([_thisGem position].x - 36, [_thisGem position].y)];
[_thisGem setGemPos:ccp([_thisGem gemPos].x-1,[_thisGem gemPos].y)];
NSLog(#"The gem position is %#", NSStringFromCGPoint([_thisGem gemPos]));
oldPos = touchLocation;
}
}
}
- (void)newGem
{
if (_thisGem) {
PCGem *oldGem = _thisGem;
NSLog(#"Old gem position at %#", NSStringFromCGPoint([oldGem gemPos]));
[oldGems addObject:oldGem];
}
_thisGem = [[PCGem alloc] initWithGemColor];
[_thisGem setPosition:ccp(160, 450)];
[self addChild:_thisGem];
[_thisGem setGemPos:ccp(4,10)];
NSLog(#"Gem added with %# color", [_thisGem gemColorName]);
}
- (void)update:(ccTime)dt
{
if ([_thisGem gemPos].y > 0) {
[self spaceBelowOccupied];
[_thisGem setPosition:ccp([_thisGem position].x, [_thisGem position].y-1)];
[_thisGem setGemPos:ccp([_thisGem gemPos].x, floor([_thisGem position].y / 36))];
} else {
[self newGem];
}
}
- (void)spaceBelowOccupied
{
for (PCGem *occupiedTile in oldGems) {
if (CGRectIntersectsRect(occupiedTile.boundingBox, _thisGem.boundingBox)) {
NSLog(#"Collision detected!");
[self newGem];
}
}
}
And my clumsy PCGem class:
- (id)initWithGemColor
{
if ((self = [super initWithFile:#"gemGS.png"])) {
NSArray *gemColorList = [NSArray arrayWithObjects:(NSString *)#"blue", (NSString *)#"red", (NSString *)#"green", nil];
NSInteger randColor = arc4random_uniform(3);
switch (randColor) {
case 0:
{
[self setGemColorName:[gemColorList objectAtIndex:0]];
ccColor3B gemColorRGB = {0,0,255};
[self setColor:gemColorRGB];
break;
}
case 1:
{
[self setGemColorName:[gemColorList objectAtIndex:1]];
ccColor3B gemColorRGB = {255,0,0};
[self setColor:gemColorRGB];
break;
}
case 2:
{
[self setGemColorName:[gemColorList objectAtIndex:2]];
ccColor3B gemColorRGB = {0,255,0};
[self setColor:gemColorRGB];
break;
}
}
}
return self;
}
Which leads me to another question, which I can't seem to find the answer to. In examples of ARC enabled Cocos2d projects, I've seen the node convenience method used, which of course is alloc]init]autorelease]. But I thought you can't use Autorelease with ARC and this would cause a crash? How does this work?
Any ideas to my woes? Would greatly appreciate clarification :)
Cheers,
Adrian

Answer 1

I think it might be caused by editing an array while enumerating through it. In your update function you call spaceBelowOccupied:
- (void)spaceBelowOccupied
{
for (PCGem *occupiedTile in oldGems) {
if (CGRectIntersectsRect(occupiedTile.boundingBox, _thisGem.boundingBox)) {
NSLog(#"Collision detected!");
[self newGem];
}
}
}
then if newGem gets called while in your for loop and this loop succeeds:
if (_thisGem) {
PCGem *oldGem = _thisGem;
NSLog(#"Old gem position at %#", NSStringFromCGPoint([oldGem gemPos]));
[oldGems addObject:oldGem];
}
then you are adding an object to an array while enumerating through it. So change your spaceBelowOccupied to this and see if it works:
- (void)spaceBelowOccupied
{
for (PCGem *occupiedTile in [oldGems copy]) {
if (CGRectIntersectsRect(occupiedTile.boundingBox, _thisGem.boundingBox)) {
NSLog(#"Collision detected!");
[self newGem];
}
}
}
that way you make a copy of oldGems to enumerate through that will get autoreleased once you are done going through it.