Using scrollViewDidScroll to handle multiple Collection View Cells

Question

I am currently animating the offset of my UICollectionView cells with scrollViewDidScroll. The Collection View previously just contained 1 UICollectionViewCell.

I just added another UICollectionViewCell to the same Collection View, and would like to perform the same animation. The problem is, I am getting a crash with error:

Precondition failed: NSArray element failed to match the Swift Array Element type. Expected DetailedCell but found BasicCell

My progress:

func scrollViewDidScroll(_ scrollView: UIScrollView) {
    // First (Detailed Cell)
    for newDetailedCell in mainCV.visibleCells as! [DetailedCell] { // Crashes on this line
        let indexPath = mainCV.indexPath(for: newDetailedCell)
        print("indexPath for Detailed Cell: \(indexPath)")
    }

    // Rest (Basic Cell)
    for basic in mainCV.visibleCells as! [BasicCell] {
        let indexPath = mainCV.indexPath(for: basic)
        print("indexPath for Basic Cell: \(indexPath)")
    }
}

How can I access visibleCells with two differet CollectionViewCells?

Answer 1

You can try

for cell in mainCV.visibleCells {
   if let res = cell as? DetailedCell {
     //
   }
   else 
   if let res = cell as? BasicCell {
     //
   }
}  

OR

let detailCells  = mainCV.visibleCells.filter { $0 is DetailedCell }  
for newDetailedCell in detailCells as! [DetailedCell] {  
    let indexPath = mainCV.indexPath(for: newDetailedCell)
    print("indexPath for Detailed Cell: \(indexPath)")
}