UICollectionView Cell not changing upon selecting - swift

Question

In my project, I have a UICollectionView. In the UICollectionView, I have a custom cell.
I am able to print the cell value when it is selected within "didSelectItemAt", however, if I try to edit the cell in any way within this method, it does not change.
I'm sure I'm missing something, any help would be appreciated!
#IBOutlet weak var collectionView: UICollectionView!
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return statValues.count
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "customCollectionViewCell", for: indexPath) as! customCollectionViewCell
cell.statLabel.text = statHeaders[indexPath.row]
cell.statLabel.textColor = UIColor(red:0.31, green:0.31, blue:0.31, alpha:1.0)
return cell
}
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "customCollectionViewCell", for: indexPath) as! customCollectionViewCell
print(cell.statLabel.text)
cell.backgroundColor = UIColor.yellow
collectionView.reloadData()
}
When user selects a cell, the code is correctly printing the value of the indexPath, however the backgroundColor does not change.

Answer 1

My guess would be that you are creating a new instance of cell instead of using the one in the collectionView
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
// Change this line
let cell = collectionView.cellForItemAtIndexPath(indexPath: indexPath)
print(cell.statLabel.text)
cell.backgroundColor = UIColor.yellow
collectionView.reloadData()
}
Also, you should probably keep an external data model for your source of truth. If you have enough collectionViews that requires scrolling, when you scroll offscreen, your cells will be reused in a random order causing cells that you did not click to be yellow.
Create a seperate array such as
var selectedStatHeaders: Set<Int>()
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "customCollectionViewCell", for: indexPath) as! customCollectionViewCell
cell.statLabel.text = statHeaders[indexPath.row]
cell.statLabel.textColor = UIColor(red:0.31, green:0.31, blue:0.31, alpha:1.0)
// Reset/configure cell each reload
if selectedStatHeaders.contains(indexPath.row) { // Can also make this into a ternary
cell.backgroundColor = UIColor.yellow
} else {
cell.backgroundColor = UIColor.whit
}
return cell
}
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
selectedStatHeaders.insert(indexPath.row)
collectionView.reloadItemsAtIndexPath(indexPath: indexpath)
}

Answer 2

Hmm... Doesn't make sense if the code is able to print but the background doesn't change color. Do you mean changing back from yellow to white? Anyway, just a hunch but I suspect it's because you are calling collectionView.reloadData() after your set the backgroundColor change.
https://developer.apple.com/documentation/uikit/uicollectionview/1618078-reloaddata
This causes the collection view to discard any currently visible
items (including placeholders) and recreate items based on the current
state of the data source object.