NSMutableArray EXC_BAD_ACCESS当我尝试从它读取

Question

我想要更新位置的粒子存储此信息我使用NSMutableArray。例如，我想每2秒更新一次。为此我尝试使用此代码。

//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]; 
} 

但是，当我在第一次调用函数运行它，并从particlesCoordinates阵列读取我有控制台消息：程序接收到的信号：“EXC_BAD_ACCESS”。我如何制定正常工作时间表？

Answer 1

[NSMutableArray arrayWithCapacity:5]返回一个自动释放实例，并在离开初始化程序一段时间后得到清理。现在指针partilesCoordinates指向未定义的内存。你需要做的：

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

或

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

Answer 2

更改此：

@property (assign, readwrite) NSMutableArray *partilesCoordinates; 

这样：

@property (nonatomic, retain) NSMutableArray *partilesCoordinates; 

并改变这一点：

partilesCoordinates = [NSMutableArray arrayWithCapacity:5]; 

到：

self.partilesCoordinates = [NSMutableArray arrayWithCapacity:5]; 

当您为“分配”属性合成一个setter时，访问器不会保留您传递它的值。