Swift project: Cannot remove an observer <CTAssetsPickerController 0x7f94862ad530>

[DeepDiving2015]

hi,
I got this issue when use CTAssetsPickerController in my swift project:

Everything is ok when I open view and pick images. But when I back to the previous view without open CTAssetsPicker view, just crashed with:
*** Terminating app due to uncaught exception 'NSRangeException', reason: 'Cannot remove an observer <CTAssetsPickerController 0x7f94862ad530> for the key path "selectedAssets" from <CTAssetsPickerController 0x7f94862ad530> because it is not registered as an observer.'

please confirm following code:

• (void)viewDidLoad
  {
  [super viewDidLoad];
  [self setupViews];
  [self setupEmptyViewController];
  [self checkAuthorizationStatus];
  [self addKeyValueObserver]; --->here to add
  }
• (void)dealloc
  {
  [self removeKeyValueObserver]; ---> should remove in "viewWillDisapear" instead of here??
  }

[tomoyuki28jp]

I get the same error when I upgrade my project from xcode6.2 to xcode6.4 (swift1.2).

*** Terminating app due to uncaught exception 'NSRangeException', reason: 'Cannot remove an observer <CTAssetsPickerController 0x134240e40> for the key path "selectedAssets" from <CTAssetsPickerController 0x134240e40> because it is not registered as an observer.'

[tomoyuki28jp]

For quick fix, adding try-catch block prevents app to crash.
tomoyuki28jp@0540a7a

[1and2papa]

@tomoyuki28jp Thanks for your PR but I need time to review and hope to find a root cause of it first.

[tomoyuki28jp]

@chiunam Thanks for your reply. I haven't created a PR yet. If you need one, please let me know :)

[1and2papa]

Hi @DeepDiving2015 and @tomoyuki28jp, may I know if this problem is still exist in Xcode 7 GM? As I have no swift projects on hand, I cannot verify the issue and make subsequence changes.

Moving removeKeyValueObserver to viewWillDisappear does not look proper to me as I always put such adding/removing code in load/dealloc or appear/disappear pair.

[DeepDiving2015]

@chiunam , I have not upgrade to Xcode 7 GM yet.
Temporarily, I add a flag to mark KeyValueObserver is added, and use it when remove.

[tomoyuki28jp]

@chiunam I confirm this problem still exists in iOS9 (Xcode7).

[1and2papa]

Hi @DeepDiving2015 & @tomoyuki28jp, this issue will be fixed in the next release.

[tomoyuki28jp]

@chiunam Thanks!!