Access collectionView from scrollViewDidEndDecelerating - ios

Question

I have a UICollectionView called dayPicker that scrolls horizontally, and lets you select the day of the month. When the user stops scrolling (scrollViewDidEndDecelerating), I want the app to do something with that day, accessible from the cell's label. All of the answers I have seen online are similar to this: https://stackoverflow.com/a/33178797/9036092
func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
var someCell : UICollectionViewCell = collectionView.visibleCells()[0];
// Other code follows...
}
When I try to access collectionView from inside the scrollViewDidEndDecelerating function, I get a Ambiguous use of collectionView error. When I substitute the actual name of my UICollectionView (dayPicker), it errors out with "Unexpectedly found nil while implicitly unwrapping an Optional value".
My question is: how do you get to collectionView from inside the scrollViewDidSomething function? Currently my scrollViewDidEndDecelerating function is inside a UICollectionViewDelegate in my view controller, and I have also tried putting it in a UIScrollViewDelegate extension.
Current code:
extension PageOneViewController: UICollectionViewDelegate {
func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
let centerPoint = CGPoint(x: UIScreen.main.bounds.midX, y: scrollView.frame.midY)
print(centerPoint) // Successfully prints the same center point every time scrolling stops
let indexPath = collectionView.indexPathForItem(at: centerPoint) // Ambiguous error
let indexPath = dayPicker.indexPathForItem(at: centerPoint) // Fatal error
}
}
Screenshot of scrollable UICollectionView in question:
I also have another method of when the user taps on the day, and it is working flawlessly. Trying to complete the experience with the scrolling ending.
Xcode 11.4.1/Swift 5

Answer 1

I figured it out, for those who come across this thread looking for the same answer. Big thanks to this answer here for a different issue: https://stackoverflow.com/a/45385718/9036092
The missing ingredient was to cast scrollView as a UICollectionView so that you can access the collectionView's cell properties.
Working code:
extension PageOneViewController: UICollectionViewDelegate {
func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
let collectionView = scrollView as! UICollectionView // This is crucial
let centerPoint = CGPoint(x: UIScreen.main.bounds.midX, y: scrollView.frame.midY)
let indexPath = collectionView.indexPathForItem(at: centerPoint)
let centerCell = collectionView.cellForItem(at: indexPath!) as! MyCustomCell
let selectedDay = centerCell.dayLabel.text //
print(selectedDay) // Prints the value of the day in the center of the collectionView, as a string
}
}