swift imageView，collectionView在展开Optional值时意外找到nil

Question

First of all: I know that there are thousands of questions about this subject and for sure in one of them my question is answered. But after hours of searching I did not find an answer which solves my problem...

I have a CollectionViewController (inside a container) and a CollectionViewCell. Inside the Cell there is an imageView. The image of the imageView has to be changed with a button in CollectionViewController.

Here is my code:

class essenCell: UICollectionViewCell {
@IBOutlet weak var Bild: UIImageView!
}

(The Cell)

class essenCollectionViewController: UICollectionViewController {
[...]
@IBAction func xyz(sender: UIButton!) {
//following: the line with the error (unexpectedly found nil while unwrapping an Optional value)
essenCell().Bild.image = UIImage(named: "erster")
}
}

(The CollectionViewController)

First I thought I could connect the Button to the Cell AND the Controller, this works theoretically but does not work in my specific case. The image change happens inside an if-Loop (inside my Controller) which refers to the parentViewController. Because I cannot use this reference inside the Cell, I need the button-function to be in the Controller.

Please help me!

Answer 1

All the setup for a collectionViewCell should be done in cellForItemAtIndexPath .

var buttonPressed = false

override func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCellWithReuseIdentifier("reuseCell", forIndexPath: indexPath) as! essenCell

    if buttonPressed {
        cell.Bild.image = UIImage(named: "erster")
    } else {
        cell.Bild.image = UIImage(named: "placeHolder")

    return cell
}

@IBAction func xyz(sender: UIButton!) {
    buttonPressed = true
    collectionView?.reloadData()
}