Change `numberOfItemsInSection` parameter of a collection view - swift

Question

How is it possible to change numberOfItemsInSection parameter of a collection view?
I have made a basic setup of a collection view. And now I try to make a button, that changes the amount of items in it.
The general setup is a standard one:
func numberOfSections(in collectionView: UICollectionView) -> Int {
1
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
arrayA.count
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath) as! CollectionViewCell
cell.imageView.image = arrayA[indexPath.item][0].image
return cell
}
The question is - how to configure a button, so it could change numberOfItemsInSection parameter from current arrayA.count to some other (e.x. arrayB.count)?
Example:

Answer 1

You could take a common a flag to toggle between arrayA and arrayB. When the button is clicked as
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return isUseArrayA ? arrayA.count : arrayB.count
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath) as! CollectionViewCell
cell.imageView.image = isUseArrayA ? arrayA[indexPath.item][0].image : arrayB[indexPath.item][0].image
return cell
}
#IBAction func changeSource(sender: UIButton) {
if sender.tag == 0 {
isUseArrayA = true
sender.tag = 1
} else {
sender.tag = 0
isUseArrayA = false
}
DispatchQueue.main.async { [weak self] in
guard let self = self else { return }
self.collectionView.reloadData()
}
}

Answer 2

// No need of numberOfSection because it is bydefault 1.
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
arrayA.count
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath) as! CollectionViewCell
cell.imageView.image = arrayA[indexPath.item][0].image
return cell
}
#IBAction func changeArrayCount(sender: UIButton) {
arrayA.append(image)
DispatchQueue.main.async { [weak self] in
guard let self = self else { return }
self.collectionView.reloadData()
}
}