iPhone - update the property of nth object of a NSMutablearray from touchesMovedwithEvent

In my earlier post in iPhone - update the property of nth object of a NSMutablearray i got something that worked in viewDidLoad but when i am trying to use almost the same code in -(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event then the application crashes.

@interface

int activeItem;
int startFrom;
NSMutableArray *iconsMutableArray;
NSMutableArray *textsMutableArray;

and then

@property int activeItem;
@property int startFrom;
- (NSMutableArray *)iconsMutableArray;
- (NSMutableArray *)textsMutableArray;


@synthesize activeItem;
@synthesize startFrom;

-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{    
    activeItem = (int)startFrom + (int)round(animationEndTo/AngleForEachItem);  
    [[iconsMutableArray objectAtIndex:activeItem] setImage:[UIImage imageNamed:[NSString stringWithFormat:@"Guide-Icon-%d_Active.png", activeItem]]];
}

But my application fails to update the UIIMageView and crashes without showing any error message. Can anyone please help me? Thanks in advance.

Below is the crash report:

Exception Type: EXC_BAD_ACCESS (SIGSEGV) Exception Codes: KERN_INVALID_ADDRESS at 0x0000000032200002 Crashed Thread: 0 Dispatch queue: com.apple.main-thread

Application Specific Information: objc_msgSend() selector name: objectAtIndex: iPhone Simulator 238.2, iPhone OS 4.3 (iPad/8F192) iPhone Simulator 238.2, iPhone OS 4.3 (iPad/8F192)

Thread 0 Crashed: Dispatch queue: com.apple.main-thread 0 libobjc.A.dylib 0x0197a09f objc_msgSend + 19 1 ??? 0x00229810 OBJC_CLASS_$_NSNumber + 0 2 UIKit 0x003b90f4 forwardMethod2 + 92 3 UIKit 0x003b90f4 forwardMethod2 + 92 4 UIKit 0x0030fd97 -[UIWindow _sendTouchesForEvent:] + 481 5 UIKit 0x002f0c37 -[UIApplication sendEvent:] + 447 6 UIKit 0x002f5f2e _UIApplicationHandleEvent + 7576 7 GraphicsServices 0x01e87992 PurpleEventCallback + 1550 8 CoreFoundation 0x017f5944 CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION + 52 9 CoreFoundation 0x01755cf7 __CFRunLoopDoSource1 + 215 10 CoreFoundation 0x01752f83 __CFRunLoopRun + 979 11 CoreFoundation 0x01752840 CFRunLoopRunSpecific + 208 12 CoreFoundation 0x01752761 CFRunLoopRunInMode + 97 13 GraphicsServices 0x01e861c4 GSEventRunModal + 217 14 GraphicsServices 0x01e86289 GSEventRun + 115 15 UIKit 0x002f9c93 UIApplicationMain + 1160 16 MJA 0x00002bde main + 96 (main.m:14) 17 MJA 0x00002b75 start + 53

Thread 1: 0 libSystem.B.dylib 0x9119d922 kevent + 10 1 libdispatch_sim.dylib 0x01d92f36 _dispatch_mgr_invoke + 237 2 libdispatch_sim.dylib 0x01d93333 _dispatch_queue_invoke + 162 3 libdispatch_sim.dylib 0x01d93593 _dispatch_worker_thread2 + 261 4 libSystem.B.dylib 0x9119cd21 _pthread_wqthread + 390 5 libSystem.B.dylib 0x9119cb66 start_wqthread + 30

Thread 2: WebThread 0 libSystem.B.dylib 0x9117709a mach_msg_trap + 10 1 libSystem.B.dylib 0x91177807 mach_msg + 68 2 CoreFoundation 0x017f5d86 __CFRunLoopServiceMachPort + 150 3 CoreFoundation 0x01752e74 __CFRunLoopRun + 708 4 CoreFoundation 0x01752840 CFRunLoopRunSpecific + 208 5 CoreFoundation 0x01752761 CFRunLoopRunInMode + 97 6 WebCore 0x02f13913 RunWebThread(void*) + 499 7 libSystem.B.dylib 0x911a47fd _pthread_start + 345 8 libSystem.B.dylib 0x911a4682 thread_start + 34

Thread 3: 0 libSystem.B.dylib 0x9117709a mach_msg_trap + 10 1 libSystem.B.dylib 0x91177807 mach_msg + 68 2 CoreFoundation 0x017f5d86 CFRunLoopServiceMachPort + 150 3 CoreFoundation 0x01752e74 __CFRunLoopRun + 708 4 CoreFoundation 0x01752840 CFRunLoopRunSpecific + 208 5 CoreFoundation 0x01752761 CFRunLoopRunInMode + 97 6 Foundation 0x0008b102 +[NSURLConnection(NSURLConnectionReallyInternal) _resourceLoadLoop:] + 398 7 Foundation 0x00055cf4 -[NSThread main] + 81 8 Foundation 0x00055c80 __NSThread__main + 1387 9 libSystem.B.dylib 0x911a47fd _pthread_start + 345 10 libSystem.B.dylib 0x911a4682 thread_start + 34

Thread 4: com.apple.CFSocket.private 0 libSystem.B.dylib 0x91196066 select$DARWIN_EXTSN + 10 1 CoreFoundation 0x017872bc __CFSocketManager + 812 2 libSystem.B.dylib 0x911a47fd _pthread_start + 345 3 libSystem.B.dylib 0x911a4682 thread_start + 34

Thread 0 crashed with X86 Thread State (32-bit): eax: 0x05e0e840 ebx: 0x05a0ef11 ecx: 0x05a05484 edx: 0x05e6b200 edi: 0x32200002 esi: 0x00229810 ebp: 0xbfffd728 esp: 0xbfffd6c4 ss: 0x0000001f efl: 0x00010202 eip: 0x0197a09f cs: 0x00000017 ds: 0x0000001f es: 0x0000001f fs: 0x00000000 gs: 0x00000037 cr2: 0x32200002

Notice this at the top of your crash log;

Exception Type: EXC_BAD_ACCESS (SIGSEGV) Exception Codes: KERN_INVALID_ADDRESS at 0x0000000032200002 Crashed Thread: 0 Dispatch queue: com.apple.main-thread

Any time you see EXC_BAD_ACCESS your first thought should be 'I've over released some object'.

As @csch said, you should turn on zombies and see what info that tells you.

My guess is that iconsMutableArray is initialized via a slice of code like this;

iconsMutableArray = [NSMutableArray array];

which assigns but does not retain (read the memory management guide here).

Also you should be using gesture recognizers instead of implementing the touch handling yourself. Read about that here.