Get indexPath from UICollectionViewController to UICollectionViewCell subclass - ios

Question

in my view controller I Am loading a custom CollectionViewCell with subclass. Based on the position of a cell's indexpath I want to format the text labels differently. I.e. first row has only one cell with bigger text, whereas the second has two cell with smaller text.
How can I access the indexpath from my UICollectionView in my UICollectionViewCell subclass? I tried a delegate protocol but this always returns nil.
Code below and Thanks so much!
Markus
UICollectionViewController:
import UIKit
protocol WorkoutDataViewControllerCVDataSource: AnyObject {
func workoutType(for workoutDataViewControllerCV: WorkoutDataViewControllerCV) -> WorkoutType
func workoutDistance(for workoutDataViewControllerCV: WorkoutDataViewControllerCV) -> Double
func workoutDuration(for workoutDataViewControllerCV: WorkoutDataViewControllerCV) -> Double
func workoutInstantVelocity(for workoutDataViewControllerCV: WorkoutDataViewControllerCV) -> Double
}
final class WorkoutDataViewControllerCV: UIViewController {
#IBOutlet weak var collectionView: UICollectionView!
weak var dataSource: WorkoutDataViewControllerCVDataSource!
private lazy var velocityFormatter = VelocityFormatter(dataSource: self, delegate: self)
private lazy var averageVelocityFormatter = VelocityFormatter(dataSource: self, delegate: self)
override func viewDidLoad() {
super.viewDidLoad()
self.collectionView.register(MeasurementCollectionViewCell.preferredNib, forCellWithReuseIdentifier: MeasurementCollectionViewCell.preferredReuseIdentifier)
}
}
// MARK: - Managing UICollectionView
extension WorkoutDataViewControllerCV: UICollectionViewDataSource {
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return 4
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Measurement Cell", for: indexPath)
return cell
}
}
extension WorkoutDataViewControllerCV: UICollectionViewDelegateFlowLayout {
func collectionView(_ collectionView: UICollectionView,
layout collectionViewLayout: UICollectionViewLayout,
sizeForItemAt indexPath: IndexPath) -> CGSize {
let availableWidth = self.view.frame.width
switch indexPath.row {
case 0: return CGSize(width: availableWidth, height: 150)
case 1: return CGSize(width: availableWidth/2.1, height: 150)
case 2: return CGSize(width: availableWidth/2.1, height: 150)
case 3: return CGSize(width: availableWidth, height: 150)
default:
return CGSize(width: availableWidth/2.1, height: 150)
}
}
}
// MARK: - Managing VelocityFormatter
extension WorkoutDataViewControllerCV: VelocityFormatterDataSource {
func duration(for velocityFormatter: VelocityFormatter) -> Double {
return dataSource.workoutDuration(for: self)
}
func distance(for velocityFormatter: VelocityFormatter) -> Double {
return dataSource.workoutDistance(for: self)
}
func instantVelocity(for velocityFormatter: VelocityFormatter) -> Double {
return dataSource.workoutInstantVelocity(for: self)
}
}
UICollectionViewCell.swift
import UIKit
final class MeasurementCollectionViewCell: UICollectionViewCell {
#IBOutlet private var measurementPropertyLabel: UILabel!
#IBOutlet private var measurementValueLabel: UILabel!
#IBOutlet private var measurementUnitLabel: UILabel!
static let preferredReuseIdentifier = "Measurement Cell"
static let preferredNib = UINib(nibName: "MeasurementCollectionViewCell", bundle: nil)
override func awakeFromNib() {
super.awakeFromNib()
updateMeasurement(property: "Speed", value: "100", unit: "km/h")
//measurementValueLabel.font = measurementValueLabel.font.monospacedDigitFont
}
func updateMeasurement(property: String, value: String, unit: String?) {
measurementPropertyLabel.text = property
measurementValueLabel.text = value
measurementUnitLabel.text = unit
}
}

Answer 1

Get the instance of cell in UICollectionView delegate method collectionView(_, didSelectItemAt _).
extension WorkoutDataViewControllerCV: UICollectionViewDelegate {
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
if let cell = collectionView.cellForItem(at: indexPath) as? MeasurementCollectionViewCell {
cell.selectedIndexPath(indexPath)
}
}
}
The indexPath will be passed as an argument in method selectedIndexPath to MeasurementCollectionViewCell from above method.
class MeasurementCollectionViewCell: UICollectionViewCell {
......
func selectedIndexPath(_ indexPath: IndexPath) {
//Do your business here.
}
}

Answer 2

You can use the responder chain to get the collection view of a cell with which you can get the index path. Just add these extensions in a new file called UICollectionViewCell+IndexPath.swift.
extension UIResponder {
func next<T: UIResponder>(_ type: T.Type) -> T? {
return next as? T ?? next?.next(type)
}
}
extension UICollectionViewCell {
var indexPath: IndexPath? {
return next(UICollectionView.self)?.indexPath(for: self)
}
}
Now inside your cell, you can use self.indexPath

Answer 3

Pretty straight forward way would be storing the indexPath into the subclass of UICollectionViewCell class. Assign it while returning from cellForRow at: index path. So now the subclassed collectionviewcell has access to the indexpath of it's own