Why app crashes with [NSObject(NSObject) doesNotRecognizeSelector:]? - swift

Question

The app sometimes crashes with [NSObject(NSObject) doesNotRecognizeSelector:], the selector being [UIImageView setImage:].
I captured it by setting an exception breakpoint and the crash happens when setting an UIImageView.image in prepareForReuse of a UICollectionViewCell:
class MyCell: UICollectionViewCell {
var coverImageView = UIImageView()
...
override func prepareForReuse() {
super.prepareForReuse()
coverImageView.image = nil
}
}
The prepareForReuse is called then the cell is instantiated:
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = myCollectionView.dequeueReusableCell(withReuseIdentifier: "myReuseID", for: indexPath) as! MyCell
...
}
Why is that happening?
Also I cannot load the quick look data view for the UIImageView so maybe the object has been released?
The error messages in console are:
2017-01-21 15:56:19.653 MyApp[4873:20387361] -[__NSMallocBlock__ size]: unrecognized selector sent to instance 0x608000880aa0
2017-01-21 15:56:37.697 MyApp[4873:20387361] invalid mode 'kCFRunLoopCommonModes' provided to CFRunLoopRunSpecific - break on _CFRunLoopError_RunCalledWithInvalidMode to debug. This message will only appear once per execution.
2017-01-21 15:56:38.847 MyApp[4873:20617657] [Optimizely Logging]: Successfully saved data file to disk. Code revision is 229
2017-01-21 15:56:42.723 MyApp[4873:20387361] [Optimizely Logging]: (ERROR) NSInvalidArgumentException: Stack Trace:
(
0 CoreFoundation 0x000000010f587d4b __exceptionPreprocess + 171
1 libobjc.A.dylib 0x000000010ef6121e objc_exception_throw + 48
2 CoreFoundation 0x000000010f5f7f04 -[NSObject(NSObject) doesNotRecognizeSelector:] + 132
3 CoreFoundation 0x000000010f50d005 ___forwarding___ + 1013
4 CoreFoundation 0x000000010f50cb88 _CF_forwarding_prep_0 + 120
5 UIKit 0x000000010ba5e20f -[UIImageView _updateImageViewForOldImage:newImage:] + 297
6 UIKit 0x000000010ba59950 -[UIImageView setImage:] + 391
7 MyApp 0x000000010945e0d8 _TFC6MyApp23MyCell15prepareForReusefT_T_ + 136
8 MyApp 0x000000010945e112 _TToFC6MyApp23MyCell15prepareForReusefT_T_ + 34
9 UIKit 0x000000010c19aed1 -[UICollectionView _dequeueReusableViewOfKind:withIdentifier:forIndexPath:viewCategory:] + 773
10 UIKit 0x000000010c19b8ea -[UICollectionView dequeueReusableCellWithReuseIdentifier:forIndexPath:] + 169
11 MyApp 0x00000001095bdee2 _TFC6MyApp23MyViewController14collectionViewfTCSo16UICollectionView13cellForItemAtV10Foundation9IndexPath_CSo20UICollectionViewCell + 594
12 MyApp 0x00000001095be747 _TToFC6MyApp23MyViewController14collectionViewfTCSo16UICollectionView13cellForItemAtV10Foundation9IndexPath_CSo20UICollectionViewCell + 87
13 UIKit 0x000000010c18675f -[UICollectionView _createPreparedCellForItemAtIndexPath:withLayoutAttributes:applyAttributes:isFocused:notify:] + 467
14 UIKit 0x000000010c186586 -[UICollectionView _createPreparedCellForItemAtIndexPath:withLayoutAttributes:applyAttributes:] + 35
15 UIKit 0x000000010c18ba5e -[UICollectionView _updateVisibleCellsNow:] + 4803
16 UIKit 0x000000010c191725 -[UICollectionView layoutSubviews] + 313
17 UIKit 0x000000010b90dab8 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 1237
18 QuartzCore 0x000000010d558bf8 -[CALayer layoutSublayers] + 146
19 QuartzCore 0x000000010d54c440 _ZN2CA5Layer16layout_if_neededEPNS_11TransactionE + 366
20 QuartzCore 0x000000010d54c2be _ZN2CA5Layer28layout_and_display_if_neededEPNS_11TransactionE + 24
21 QuartzCore 0x000000010d4da318 _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 280
22 QuartzCore 0x000000010d5073ff _ZN2CA11Transaction6commitEv + 475
23 QuartzCore 0x000000010d507d6f _ZN2CA11Transaction17observer_callbackEP19__CFRunLoopObservermPv + 113
24 CoreFoundation 0x000000010f52c267 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 23
25 CoreFoundation 0x000000010f52c1d7 __CFRunLoopDoObservers + 391
26 CoreFoundation 0x000000010f510f8e __CFRunLoopRun + 1198
27 CoreFoundation 0x000000010f510884 CFRunLoopRunSpecific + 420
28 GraphicsServices 0x0000000112b77a6f GSEventRunModal + 161
29 UIKit 0x000000010b848c68 UIApplicationMain + 159
30 MyApp 0x00000001092f5a7f main + 111
31 libdyld.dylib 0x00000001115b568d start + 1
)
2017-01-21 15:56:42.725 MyApp[4873:20387361] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSMallocBlock__ size]: unrecognized selector sent to instance 0x608000880aa0'
*** First throw call stack:
(
0 CoreFoundation 0x000000010f587d4b __exceptionPreprocess + 171
1 libobjc.A.dylib 0x000000010ef6121e objc_exception_throw + 48
2 CoreFoundation 0x000000010f5f7f04 -[NSObject(NSObject) doesNotRecognizeSelector:] + 132
3 CoreFoundation 0x000000010f50d005 ___forwarding___ + 1013
4 CoreFoundation 0x000000010f50cb88 _CF_forwarding_prep_0 + 120
5 UIKit 0x000000010ba5e20f -[UIImageView _updateImageViewForOldImage:newImage:] + 297
6 UIKit 0x000000010ba59950 -[UIImageView setImage:] + 391
7 MyApp 0x000000010945e0d8 _TFC6MyApp23MyCell15prepareForReusefT_T_ + 136
8 MyApp 0x000000010945e112 _TToFC6MyApp23MyCell15prepareForReusefT_T_ + 34
9 UIKit 0x000000010c19aed1 -[UICollectionView _dequeueReusableViewOfKind:withIdentifier:forIndexPath:viewCategory:] + 773
10 UIKit 0x000000010c19b8ea -[UICollectionView dequeueReusableCellWithReuseIdentifier:forIndexPath:] + 169
11 MyApp 0x00000001095bdee2 _TFC6MyApp23MyViewController14collectionViewfTCSo16UICollectionView13cellForItemAtV10Foundation9IndexPath_CSo20UICollectionViewCell + 594
12 MyApp 0x00000001095be747 _TToFC6MyApp23MyViewController14collectionViewfTCSo16UICollectionView13cellForItemAtV10Foundation9IndexPath_CSo20UICollectionViewCell + 87
13 UIKit 0x000000010c18675f -[UICollectionView _createPreparedCellForItemAtIndexPath:withLayoutAttributes:applyAttributes:isFocused:notify:] + 467
14 UIKit 0x000000010c186586 -[UICollectionView _createPreparedCellForItemAtIndexPath:withLayoutAttributes:applyAttributes:] + 35
15 UIKit 0x000000010c18ba5e -[UICollectionView _updateVisibleCellsNow:] + 4803
16 UIKit 0x000000010c191725 -[UICollectionView layoutSubviews] + 313
17 UIKit 0x000000010b90dab8 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 1237
18 QuartzCore 0x000000010d558bf8 -[CALayer layoutSublayers] + 146
19 QuartzCore 0x000000010d54c440 _ZN2CA5Layer16layout_if_neededEPNS_11TransactionE + 366
20 QuartzCore 0x000000010d54c2be _ZN2CA5Layer28layout_and_display_if_neededEPNS_11TransactionE + 24
21 QuartzCore 0x000000010d4da318 _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 280
22 QuartzCore 0x000000010d5073ff _ZN2CA11Transaction6commitEv + 475
23 QuartzCore 0x000000010d507d6f _ZN2CA11Transaction17observer_callbackEP19__CFRunLoopObservermPv + 113
24 CoreFoundation 0x000000010f52c267 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 23
25 CoreFoundation 0x000000010f52c1d7 __CFRunLoopDoObservers + 391
26 CoreFoundation 0x000000010f510f8e __CFRunLoopRun + 1198
27 CoreFoundation 0x000000010f510884 CFRunLoopRunSpecific + 420
28 GraphicsServices 0x0000000112b77a6f GSEventRunModal + 161
29 UIKit 0x000000010b848c68 UIApplicationMain + 159
30 MyApp 0x00000001092f5a7f main + 111
31 libdyld.dylib 0x00000001115b568d start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException

Answer 1

I think the problem is that you are not calling the designated initializer of UIImageView, therefore its image property is not properly initialized and trying to assign to it crashes the app:
-[NSMallocBlock size]: unrecognized selector sent to instance 0x608000880aa0
The method tries to call the size method on the old image but the old image was set to some random memory address.
To fix it, initialize UIImageView properly using the designated initializer:
var coverImageView = UIImageView(image: nil)