Why is my UICollectionViewCell not getting data from UICollectionViewController? - ios

Question

I have a UICollectionViewController called SwipingController that creates a TeamCell and gives it a teamName of "Boston Celtics"
class SwipingController: UICollectionViewController, UICollectionViewDelegateFlowLayout {
override func viewDidLoad() {
super.viewDidLoad()
collectionView?.backgroundColor = .white
collectionView?.register(TeamCell.self, forCellWithReuseIdentifier: "cellId")
collectionView?.isPagingEnabled = true
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {
return 0
}
override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return 2
}
override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cellId", for: indexPath) as! TeamCell
cell.teamName = "Boston Celtics"
return cell
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
return CGSize(width: view.frame.width, height: view.frame.height)
}
}
However, when I run the code, teamName still prints out as an empty string.
class TeamCell: UICollectionViewCell {
var teamName: String = ""
override init(frame: CGRect) {
super.init(frame: frame)
print(teamName) //this prints nothing
}
}

Answer 1

let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cellId", for: indexPath) as! TeamCell
it inits the cell, and so initially it is empty.
After initialization cell.teamName = "Boston Celtics" is called, actually having no effect
you have to update the name
class TeamCell: UICollectionViewCell {
var teamName: String = ""
override init(frame: CGRect) {
super.init(frame: frame)
print(teamName) //this prints nothing
}
func updateName(name : String) {
self.testName = name
}
}
in collectionview
override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cellId", for: indexPath) as! TeamCell
cell.updateName(name : "Boston Celtics")
return cell
}

Answer 2

You are simply looking at teamName too early in the process. By the time cellForItemAt hits the cell.teamName = ... line, the cell’s init method has already been called. So, teamName will always be blank during the init method. But, teamName will be set before the cell appears within the view.
Often cells would just have UIKit controls, such as a UILabel, and you’d set the text of that, e.g.
class TeamCell: UICollectionViewCell {
var teamLabel: UILabel = {
let label = UILabel()
label.translatesAutoresizingMaskIntoConstraints = false
return label
}()
override init(frame: CGRect) {
super.init(frame: frame)
configure()
}
required init?(coder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
func configure() {
addSubview(teamLabel)
NSLayoutConstraint.activate([
teamLabel.centerXAnchor.constraint(equalTo: centerXAnchor),
teamLabel.centerYAnchor.constraint(equalTo: centerYAnchor)
])
}
func update(for team: String) {
teamLabel.text = team
}
}
And then
override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cellId", for: indexPath) as! TeamCell
cell.update(for: "Boston Celtics")
return cell
}

Answer 3

Please try this :
class TeamCell: UICollectionViewCell {
var teamName : String = "" {
didSet {
print(teamName)
}
}
override func awakeFromNib() {
super.awakeFromNib()
//custom logic goes here
}
}
override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cellId", for: indexPath) as! TeamCell
cell.teamName = "Boston Celtics"
return cell
}
OR
class TeamCell: UICollectionViewCell {
override func awakeFromNib() {
super.awakeFromNib()
//custom logic goes here
}
func getTeamName(teamName : String)
{
print(teamName)
}
}
override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cellId", for: indexPath) as! TeamCell
cell.getTeamName(teamName: "Boston Celtics")
return cell
}

Answer 4

in TeamCell class try this
var teamcell = String()
override init(frame: CGRect) {
super.init(frame: frame)
if teamcell != nil {
print(teamName)
}
}

Answer 5

It’s just a matter of order of events. The cell is created, you print, the cell is used in the table view, the team name is assigned.