Enumerating over children and removing them

(2 posts) (1 voice)

Started 1 year ago by enbr
Latest reply from enbr

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Hi, I'm having trouble figuring out a replacement for this code. I thought it was working, but it is erroring now because I'm modifying self while enumerating through it. Any ideas?
Thanks in advance.

- (void)removeAllSquares {
	for (Square *square in self) {
		if ([square isKindOfClass:[Square class]]) {
			[self removeChild:square];
		}
	}
}

Also, here is the error I get...

2011-03-09 19:30:26.047 Squares[710:207] *** Terminating app due to uncaught exception 'NSGenericException', reason: '*** Collection <Play: 0x5bedf90> was mutated while being enumerated.<Play: 0x5bedf90>'
*** Call stack at first throw:
(
	0   CoreFoundation                      0x01343be9 __exceptionPreprocess + 185
	1   libobjc.A.dylib                     0x014985c2 objc_exception_throw + 47
	2   CoreFoundation                      0x013436a9 __NSFastEnumerationMutationHandler + 377
	3   Squares                             0x000050c4 -[Play removeAllSquares] + 159
	4   Squares                             0x000051cf -[Play gameOverForReason:] + 36
	5   Squares                             0x000080b7 -[Square bombTimerDone:] + 114
	6   CoreFoundation                      0x012b467d __invoking___ + 29
	7   CoreFoundation                      0x012b4551 -[NSInvocation invoke] + 145
	8   Squares                             0x0001f67f -[SPEventDispatcher dispatchEvent:] + 593
	9   Squares                             0x0002391f -[SPTween advanceTime:] + 2780
	10  Squares                             0x00024727 -[SPJuggler advanceTime:] + 347
	11  Squares                             0x00017e09 -[SPStage advanceTime:] + 76
	12  Squares                             0x00020e4e -[SPView renderStage] + 214
	13  QuartzCore                          0x00dee6a8 _ZN2CA7Display11DisplayLink8dispatchEyy + 128
	14  QuartzCore                          0x00dee7ed _ZN2CA7Display19EmulatorDisplayLink8callbackEP16__CFRunLoopTimerPv + 145
	15  CoreFoundation                      0x01324fe3 __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ + 19
	16  CoreFoundation                      0x01326594 __CFRunLoopDoTimer + 1220
	17  CoreFoundation                      0x01282cc9 __CFRunLoopRun + 1817
	18  CoreFoundation                      0x01282240 CFRunLoopRunSpecific + 208
	19  CoreFoundation                      0x01282161 CFRunLoopRunInMode + 97
	20  GraphicsServices                    0x01bfc268 GSEventRunModal + 217
	21  GraphicsServices                    0x01bfc32d GSEventRun + 115
	22  UIKit                               0x0033442e UIApplicationMain + 1160
	23  Squares                             0x00002796 main + 104
	24  Squares                             0x00002725 start + 53
)
terminate called after throwing an instance of 'NSException'

Posted 1 year ago #

enbr
Moderator

Yay, this code is working great!
Is there a better way to do this?

- (void)removeAllSquares {
	NSMutableArray *toRemove = [[NSMutableArray alloc] init];
	for (Square *square in self) {
		if ([square isKindOfClass:[Square class]]) {
			[toRemove addObject:square];
		}
	}
	for (Square *square in toRemove) {
		[self removeChild:square];
	}
	[toRemove release];
}

UPDATE: I created a PlayObjectContainer class to hold all of the Squares for me.
Now I can just call:

[container removeAllChildren];

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Enumerating over children and removing them

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