UICollection NumberOfItemsInSections issue with adding a constant to vars - ios

Question

I have two different cell type classes and i'm trying to make the first indexpath with the class PayNowCell, have it remain displayed. While the other cells are of class CheckOutCell. Now the problem is in my func numberofitemsinsection. Currently i'm using return checkout.count but it missing the PayNowCell when view loads. If i make it return checkout.count+1 to always have the PayNowCell available; my program crashes giving me the error index out of bounds. The array checkout is a global var. Can someone explain why and provide a fix? Been stuck on this for a while. Code Below.
class CheckoutController: UICollectionViewCell, UICollectionViewDataSource, UICollectionViewDelegate, UICollectionViewDelegateFlowLayout {
var inventoryTabController: InventoryTabController?
override init(frame: CGRect){
super.init(frame: frame)
setupViews()
NotificationCenter.default.addObserver(forName: .arrayValueChanged, object: nil, queue: OperationQueue.main) { [weak self] (notif) in
self?.collectionView.reloadData()
}
}
deinit {
NotificationCenter.default.removeObserver(self)
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
func loadItems() -> [Item]? {
return NSKeyedUnarchiver.unarchiveObject(withFile: Item.ArchiveURL.path) as? [Item]
}
func saveItems() {
let isSuccessfulSave = NSKeyedArchiver.archiveRootObject(checkout, toFile: Item.ArchiveURL.path)
if !isSuccessfulSave {
print("Failed to save items...")
}
}
func addItem(item: Item) {
items.append(item)
collectionView.reloadData()
}
func editItem(item: Item, index: Int) {
items[index] = item
collectionView.reloadData()
}
func prepare(for segue: UIStoryboardSegue, sender: Any?) {
// Identify which segue is occuring.
if segue.identifier == "ShowDetail" {
let itemDetailViewController = segue.destination as! AddItemController
// Get the cell that generated this segue.
if let selectedItemCell = sender as? InventoryCell {
let indexPath = collectionView.indexPath(for: selectedItemCell)!
let selectedItem = items[indexPath.row]
itemDetailViewController.item = selectedItem
}
}
else if segue.identifier == "AddItem" {
print("Adding new meal.")
}
}
lazy var collectionView: UICollectionView = {
let layout = UICollectionViewFlowLayout()
let cv = UICollectionView(frame: .zero, collectionViewLayout: layout)
cv.dataSource = self
cv.delegate = self
cv.backgroundColor = UIColor.rgb(r: 247, g: 247, b: 247)
return cv
}()
let cellId = "cellId"
let paynow = "paynow"
func setupViews() {
backgroundColor = .brown
addSubview(collectionView)
addConstraintsWithFormat("H:|[v0]|", views: collectionView)
addConstraintsWithFormat("V:|[v0]|", views: collectionView)
collectionView.indicatorStyle = UIScrollViewIndicatorStyle.white
collectionView.register(PayNowCell.self, forCellWithReuseIdentifier: paynow)
collectionView.register(CheckoutCell.self, forCellWithReuseIdentifier: cellId)
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return checkout.count //init number of cells
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
if indexPath.item == 0 {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "paynow", for: indexPath) as! PayNowCell //init cells
return cell
}else{
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cellId", for: indexPath) as! CheckoutCell //init cells
print("Printing this \(checkout.count)")
cell.item = checkout[indexPath.item]
return cell
}
}
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
//let item = items[indexPath.item]
//inventoryController?.showItemDetailForItem(item: item, index: indexPath.item)
print("selected")
print(indexPath.item)
collectionView.reloadData()
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
if indexPath.item == 0 {
return CGSize(width:frame.width, height: 100) //each cell dimensions
}else{
return CGSize(width:frame.width, height: 150) //each cell dimensions
}
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {
return 0
}

Answer 1

It's better to re-arrange your collection view to have 2 sections:
Section 0: PayNow cell (only 1 cell)
Section 1: Checkout cells (using checkout array list)
Then you don't have any confusion about the indexPath.item issue.
func numberOfSections(in collectionView: UICollectionView) -> Int {
return 2
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return section == 0 ? 1 : checkout.count
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
if indexPath.section == 0 {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "paynow", for: indexPath) as! PayNowCell //init cells
return cell
} else {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cellId", for: indexPath) as! CheckoutCell //init cells
print("Printing this \(checkout.count)")
cell.item = checkout[indexPath.item]
return cell
}
}

Answer 2

You need to subtract 1 from your cellForRow function. Since you are adding the PayNowCell you are adding one extra indexPath, but currently, you are using the default indexPath given by the dataSource function. That index will always be one higher than the count of your items. By subtracting 1 from the indexPath, you will be back in sync with your itemsArray, taking into account the PayNowCell.
cell.item = checkout[indexPath.item - 1]