UICollectionView和Supplementary View崩溃

Question

I have a UICollectioView that works fine. There are 2 ways to get to this page.

1. though the app.
2. tap on push notification.

Everything works good except one case.

if the user is in the chat and then he exits the app (home button) then he gets a push notification he presses it and the the app crashes.

crash:

2015-09-25 10:28:15.140 Quest[298:16922] * Assertion failure in -[UICollectionView _createPreparedSupplementaryViewForElementOfKind:atIndexPath:withLayoutAttributes:applyAttributes:], /BuildRoot/Library/Caches/com.apple.xbs/Sources/UIKit/UIKit-3505.16/UICollectionView.m:1519 2015-09-25 10:28:15.146 Quest[298:16922] * Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'UICollectionView dataSource is not set' *** First throw call stack: (0x1828b4f5c 0x1973b7f80 0x1828b4e2c 0x1837a3f3c 0x187f97a38 0x187e6ebd4 0x187e6fb54 0x187e69b88 0x187e0700c 0x18760df14 0x187608b20 0x1876089e0 0x18760807c 0x187607dd0 0x1880c0bd4 0x18286c48c 0x18286bdc4 0x182869d4c 0x182798dc0 0x18d8ec088 0x187e72f60 0x100215590 0x197be28b8) libc++abi.dylib: terminating with uncaught exception of type NSException

code in push handler:

func application(application: UIApplication, didReceiveRemoteNotification userInfo: [NSObject : AnyObject]) {

                let home = storyboard.instantiateViewControllerWithIdentifier("home") as! HomeViewController
                let chat = storyboard.instantiateViewControllerWithIdentifier("chat") as! ChatViewController

                var controllers : [UIViewController] = [login, chat]
                NotificationManager.handleNotification(userInfo, controllers: &controllers, storyboard: storyboard)
                navC.viewControllers = controllers
                self.window?.makeKeyAndVisible()

}

collectioview setting code

@IBOutlet weak var chatCollectionView: UICollectionView! {
    didSet {
        chatCollectionView.registerNib(UINib(nibName: "ChatTimeStampCollectionViewCell", bundle: nil), forCellWithReuseIdentifier: "ChatTimeStampCell")
        chatCollectionView.registerNib(UINib(nibName: "ChatReceiverCollectionViewCell", bundle: nil), forCellWithReuseIdentifier: "ChatReceiverCell")
        chatCollectionView.registerNib(UINib(nibName: "ChatSenderCollectionViewCell", bundle: nil), forCellWithReuseIdentifier: "ChatSenderCell")
        chatCollectionView.registerNib(UINib(nibName: "ChatHeaderCollectionReusableView", bundle: nil), forSupplementaryViewOfKind: UICollectionElementKindSectionHeader, withReuseIdentifier: "ChatHeaderCell")

        chatCollectionView.dataSource = self
        chatCollectionView.delegate = self
    }
}

Answer 1

If you are using custom layout in your collection view, check if its datasource is nil in:

- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect

The result should look something like this:

- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect
    if (self.collectionView.dataSource != nil) {
        // Your layout code    
        return array;
    }
    return nil;
}

This change resolves the following issue:

• Assertion failure in -[UICollectionView _createPreparedSupplementaryViewForElementOfKind:atIndexPath:withLayoutAttributes:applyAttributes:]

You can also check the following topics, however they didn't resolve anything in my case: UICollectionView and Supplementary View (header)

Removing empty space, if the section header is hidden in the UICollectionView

Hope it will help you, and you won't waste as much time as I did. @eeeee thank you for pointing me in the right direction.