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:

CodePudding user response：

// 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()
    }
}

CodePudding user response：

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()
    }
}