Swift: UICollectionView sizeForItemAt will never be executed - ios

Question

I'm making a CollectionView which has 2 sections, everything is fine but the size. I'd like to give different size of cell in different section, but when I call sizeForItemAt, Xcode shows a yellow warning "Will never be executed". Here's how I set my CollectionView functions:
extension ArtistProfileViewController: UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {
func numberOfSections(in collectionView: UICollectionView) -> Int {
return 2
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
switch mySections[section] {
case .profile:
return 1
case .relatedArtists:
return 10
}
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
switch mySections[indexPath.section] {
case .profile:
guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: ArtistProfileCell.identifier, for: indexPath) as? ArtistProfileCell else { return UICollectionViewCell()}
return cell
case .relatedArtists:
guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: RelatedArtistCell.identifier, for: indexPath) as? RelatedArtistCell else { return UICollectionViewCell()}
cell.myImageView.image = UIImage(systemName: "person")
return cell
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
return CGSize(width: 100, height: 100)
}
}
And here is how I set my CollectionView:
var myCollectionView: UICollectionView = {
let layout = UICollectionViewFlowLayout()
layout.scrollDirection = .vertical
layout.estimatedItemSize = .zero
let cv = UICollectionView(frame: .zero, collectionViewLayout: layout)
cv.register(ArtistProfileCell.self, forCellWithReuseIdentifier: ArtistProfileCell.identifier)
cv.register(RelatedArtistCell.self, forCellWithReuseIdentifier: RelatedArtistCell.identifier)
return cv
}()
I did set the CollectionView.delegate/datasource to self in viewDidLoad, and I can see the cell appear on the screen. However, the size of cell does not change at all. Plus, I know one of the solution is to set the estimated size to none in storyboard, but I don't know how to set it programmatically. So I don't know if it works.
There's one thing odd, when I call sizeForItemAt, it does not show the complete function automatically. I have to type it by myself like this.
Does anyone can help? Thanks in advance!

Answer 1

You put sizeForItemAt inside cellForItemAt. They need to be separate.
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
switch mySections[indexPath.section] {
case .profile:
guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: ArtistProfileCell.identifier, for: indexPath) as? ArtistProfileCell else { return UICollectionViewCell()}
return cell
case .relatedArtists:
guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: RelatedArtistCell.identifier, for: indexPath) as? RelatedArtistCell else { return UICollectionViewCell()}
cell.myImageView.image = UIImage(systemName: "person")
return cell
}
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
return CGSize(width: 100, height: 100)
}
Try selecting your code, then pressing Ctrl + i to re-format your code (fixes indenting too!)