How to delete item from collection view?

Question

I try to remove an item from a collection view based on a user's choice in an alert.

I have the following code:

func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {
    let person = people[indexPath.item]

    let questionController = UIAlertController(title: "What u wanna do?", message: nil, preferredStyle: .Alert)
    questionController.addAction(UIAlertAction(title: "Rename person", style: .Default, handler: {

        (action:UIAlertAction!) -> Void in

        let ac = UIAlertController(title: "Rename person", message: nil, preferredStyle: .Alert)
        ac.addTextFieldWithConfigurationHandler(nil)

        ac.addAction(UIAlertAction(title: "Cancel", style: .Cancel, handler: nil))
        ac.addAction(UIAlertAction(title: "OK", style: .Default) { [unowned self, ac] _ in
            let newName = ac.textFields![0] as! UITextField
            person.name = newName.text

            self.collectionView.reloadData() })

        self.presentViewController(ac, animated: true, completion: nil)

    }))

    questionController.addAction(UIAlertAction(title: "Delete Person", style: .Default, handler: {

        (action:UIAlertAction!) -> Void in

        println("hello world")
        self.collectionView.deleteItemsAtIndexPaths([indexPath.item])
        self.collectionView.reloadData()

    }))

    presentViewController(questionController, animated: true, completion: nil)
}

"hello world" works okay but the app crashes when I press "Delete Person".

The console output is

hello world
2015-07-18 13:40:14.628 Project10[15888:1274436] -[__NSCFNumber section]:         unrecognized selector sent to instance 0xb000000000000003
2015-07-18 13:40:14.636 Project10[15888:1274436] *** Terminating app due to    uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFNumber    section]: unrecognized selector sent to instance 0xb000000000000003'

What am I doing wrong?

Answer 1

You should change

self.collectionView.deleteItemsAtIndexPaths([indexPath.item])

to

self.collectionView.deleteItemsAtIndexPaths([indexPath])

deleteItemsAtIndexPaths expects an array of NSIndexPaths, not an array of numbers.

Besides that, if you call deleteItemsAtIndexPaths you don't need a call to reloadData - this will even prevent any animation from happening.

Don't forget to update your data source - the person has to be removed from the people array.

people.removeAtIndex(indexPath.item)

Do this before calling deleteItemsAtIndexPaths.