ERROR: Attempt to insert item 0 into section 0, but there are only 0 items in section 0 after the update

Question

My code:

    DataService.dataService.fetchDataFromServer { (channel) in
        self.channels.append(channel)
        let indexPath = IndexPath(item: self.channels.count - 1, section: 0)
        self.collectionView?.insertItems(at: [indexPath])
    }

Fetch Data From Server Function:

 func fetchDataFromServer(callBack: @escaping (Channel) -> ()) {
        DataService.dataService.CHANNEL_REF.observe(.childAdded, with: { (snapshot) in
            let channel = Channel(key: snapshot.key, snapshot: snapshot.value as! Dictionary<String, AnyObject>)
            callBack(channel)
        })
    }

Number of Items Section:

override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    // #warning Incomplete implementation, return the number of items
    return 0
}

The Full Error:

Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'attempt to insert item 0 into section 0, but there are only 0 items in section 0 after the update'

I am working with a collection view and have no clue why this error is showing up.

Any help would be appreciated!

Answer 1

Your numberOfItemsInSection is returning 0, so when tell the collection view you are adding an item, it gets upset when this method says that there are still 0 items in the collection.

Your code even has a comment // #warning Incomplete implementation, return the number of items

You probably want something like:

override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {

    return self.channels.count
}