NSMutableArray EXC_BAD_ACCESS when i try read from it

Question

I want update position of Particles for store this information I use NSMutableArray. I want do update 1 time per 2 seconds for example. For this I try use this code.

//ParticlesLayer.h
@interface ParticlesLayer : CCLayer {
CCQuadParticleSystem *particle;
NSMutableArray *partilesCoordinates;
}

@property (assign, readwrite) NSMutableArray *partilesCoordinates;
-(void)partilesMove:(ccTime)dt;
-(void)particleInit;

//ParticlesLayer.m
@implementation ParticlesLayer

@synthesize partilesCoordinates;

-(id) init {
self = [super init];
    partilesCoordinates = [NSMutableArray arrayWithCapacity:5];
    [partilesCoordinates addObject: [NSValue valueWithCGPoint:ccp(67,152)]];
    [partilesCoordinates addObject: [NSValue valueWithCGPoint:ccp(140,147)]];
    [partilesCoordinates addObject: [NSValue valueWithCGPoint:ccp(198,100)]];
    [partilesCoordinates addObject: [NSValue valueWithCGPoint:ccp(261,126)]];
    [partilesCoordinates addObject: [NSValue valueWithCGPoint:ccp(364,135)]];
    // bla bla bla
    //...
    //bla bla bla
    [self schedule:@selector(partilesMove:) interval:2];
    return self;
} 

-(void)emittersMove:(ccTime)dt{
    NSMutableArray *newParticlesCoordinates = [NSMutableArray arrayWithCapacity:5];
    CGPoint newPoint;
    for (int i = 0; i < 5; ++i) {
        [self particleInit];
        NSLog(@"%@", [particlesCoordinates objectAtIndex:i]); // on this part of code i have problem
        particle.position = [[particlesCoordinates objectAtIndex:i] CGPointValue];
        [self addChild:emitter];
        newPoint = emitter.position;
        newPoint.x += 15;
        newPoint.y += 15;
        [newParticlesCoordinates addObject:[NSValue valueWithCGPoint:newPoint]];
    }
    [partilesCoordinates removeAllObjects];
    [partilesCoordinates newParticlesCoordinates];
    [newParticlesCoordinates removeAllObjects];
}

But when i run it on first calling function and reading from particlesCoordinates array i have console message : Program received signal: "EXC_BAD_ACCESS". How I can make normal-working schedule?

Answer 1

Change this:

@property (assign, readwrite) NSMutableArray *partilesCoordinates;

to this:

@property (nonatomic, retain) NSMutableArray *partilesCoordinates;

and change this:

partilesCoordinates = [NSMutableArray arrayWithCapacity:5];

to:

self.partilesCoordinates = [NSMutableArray arrayWithCapacity:5];

When you synthesize a setter for an "assign" property, the accessor won't retain the value you pass it.

Answer 2

[NSMutableArray arrayWithCapacity:5] returns an autoreleased instance, and that gets cleaned up some time after leaving the initializer. Now the pointer partilesCoordinates points to undefined memory. You need to do:

partilesCoordinates = [[NSMutableArray arrayWithCapacity:5] retain];

or

partilesCoordinates = [[NSMutableArray alloc] initWithCapacity:5];