Dynamic Size for NSCollectionViewItem

Question

I am trying to give a dynamic size to my NSCollectionViewItem. I want them to have a size determine by their content and the constraint I defined.

For that I have add to my viewcontroller which holds the NSCollectionView the following :

extension ViewController :  NSCollectionViewDelegateFlowLayout {
    func collectionView(_ collectionView: NSCollectionView, layout collectionViewLayout: NSCollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> NSSize{

        let item = collectionView.item(at: indexPath)
        if let viewItem = item as NSCollectionViewItem? {
            return viewItem.view.fittingSize
        }

        return NSSize(width: 200, height: 100)

    }
}

Which throw an exception.

An uncaught exception was raised
*** -[__NSArrayM objectAtIndex:]: index 1 beyond bounds [0 .. 0]

I don't see where it come from, I tried to catch it but xcode says that item(at:) don't throws exception.

Edit: but in fact it does, I had an exception breakpoint and it break in item(at:)

Beside sending a bug repport to Apple does someone have an other idea ? And since item(at:) is not supposed to throw error a do catch bloc is ineffective

Try this. https://stackoverflow.com/questions/46286020/nscollectionview-sizeforitemat-always-returning-exception-when-trying-to-referen/59319607#59319607 — Owen Zhao, Dec 13 '19 at 09:32

score 0 · Answer 1 · answered Sep 06 '17 at 16:59

0

As you mention, I Don't think this method is crashing. From the documentation:

Return: The item for the specified index path or nil if no item is available.

Have you try to add an exception breakpoint? You should see where it's crashing.

answered Sep 06 '17 at 16:59

Rémy Virin

3,379
23
42

score 0 · Answer 2 · answered Aug 08 '18 at 21:06

0

sizeForItemAtIndexPath calling before creating a UICollectionViewItem, so it's impossible to do it.

answered Aug 08 '18 at 21:06

Tony AH

51
6

Dynamic Size for NSCollectionViewItem

2 Answers2