Swift collectionview cant automatically select first cell when load - ios

Question

so i have collectionview where i want the first cell of the collectionview cell is selected when the view is load, i try to use viewDidAppear method and.....well not work very good.
cause for the very first time i try to load the view the first collectionview cell is not selected, but when i back to previous controller and then tap back to the collectionview controller, the first cell of the collectionview is selected.
i mean i dont know what i have to go back and forth so the first cell can automatically be selected.
heres my code :
#IBOutlet weak var katalogColView: UICollectionView!
let indexPos = NSIndexPath(row: 0, section: 0) as IndexPath
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
self.katalogColView.selectItem(at: indexPos, animated: false, scrollPosition: [])
self.collectionView(katalogColView, didSelectItemAt: indexPos)
}
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
if collectionView == katalogColView {
guard let cell = collectionView.cellForItem(at: indexPath) as? KatalogCell else {return}
cell.indicator.backgroundColor = #colorLiteral(red: 0.9916914105, green: 0.2737390399, blue: 0.284696877, alpha: 1)
cell.katalogText.textColor = #colorLiteral(red: 0, green: 0, blue: 0, alpha: 1)
}
func collectionView(_ collectionView: UICollectionView, didDeselectItemAt indexPath: IndexPath) {
if collectionView == katalogColView {
guard let cell = collectionView.cellForItem(at: indexPath) as? KatalogCell else {return}
cell.indicator.backgroundColor = #colorLiteral(red: 1, green: 1, blue: 1, alpha: 1)
cell.katalogText.textColor = #colorLiteral(red: 0.3950070143, green: 0.4162634611, blue: 0.4362195134, alpha: 1)
}
}
so the code is when the cell is selected, there's a uiview indicator that colored red if selected, and white if not selected
is there something wrong with my code? i mean of course there's something wrong but can anyone tell me why its not working?
i mean like i said it only work if i go back to previous controller, and then i go back to that collectionView controller where it automatically selected first cell, but not selected automatically at the first time i load the controller.
Thanks

Answer 1

Add these lines in cell class and try:
override var isSelected: Bool {
didSet {
if isSelected {
indicator.backgroundColor = #colorLiteral(red: 0.9916914105, green: 0.2737390399, blue: 0.284696877, alpha: 1)
katalogText.textColor = #colorLiteral(red: 0, green: 0, blue: 0, alpha: 1)
}else {
indicator.backgroundColor = #colorLiteral(red: 1, green: 1, blue: 1, alpha: 1)
katalogText.textColor = #colorLiteral(red: 0.3950070143, green: 0.4162634611, blue: 0.4362195134, alpha: 1)
}
}
}

Answer 2

You have to select it from visibleCells.
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(true)
let selectedIndex = collectionView.indexPathsForVisibleItems![0]
collectionView.selectItem(at: selectedIndex, animated: true, scrollPosition: .none)
}