Swift - How do I decode json from a REST API - ios

Question

I am trying to make a GET from a REST API in swift. When I use the print statement (print(clubs)) I see the expected response in the proper format. But in the VC is gives me an empty array.
Here is the code to talk to the API
extension ClubAPI {
public enum ClubError: Error {
case unknown(message: String)
}
func getClubs(completion: #escaping ((Result<[Club], ClubError>) -> Void)) {
let baseURL = self.configuration.baseURL
let endPoint = baseURL.appendingPathComponent("/club")
print(endPoint)
API.shared.httpClient.get(endPoint) { (result) in
switch result {
case .success(let response):
let clubs = (try? JSONDecoder().decode([Club].self, from: response.data)) ?? []
print(clubs)
completion(.success(clubs))
case .failure(let error):
completion(.failure(.unknown(message: error.localizedDescription)))
}
}
}
}
and here is the code in the VC
private class ClubViewModel {
#Published private(set) var clubs = [Club]()
#Published private(set) var error: String?
func refresh() {
ClubAPI.shared.getClubs { (result) in
switch result {
case .success(let club):
print("We have \(club.count)")
self.clubs = club
print("we have \(club.count)")
case .failure(let error):
self.error = error.localizedDescription
}
}
}
}
and here is the view controller code (Before the extension)
class ClubViewController: UIViewController {
private var clubs = [Club]()
private var subscriptions = Set<AnyCancellable>()
private lazy var dataSource = makeDataSource()
enum Section {
case main
}
private var errorMessage: String? {
didSet {
}
}
private let viewModel = ClubViewModel()
#IBOutlet private weak var tableView: UITableView!
override func viewDidLoad() {
super.viewDidLoad()
self.subscriptions = [
self.viewModel.$clubs.assign(to: \.clubs, on: self),
self.viewModel.$error.assign(to: \.errorMessage, on: self)
]
applySnapshot(animatingDifferences: false)
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
self.viewModel.refresh()
}
}
extension ClubViewController {
typealias DataSource = UITableViewDiffableDataSource<Section, Club>
typealias Snapshot = NSDiffableDataSourceSnapshot<Section, Club>
func applySnapshot(animatingDifferences: Bool = true) {
// Create a snapshot object.
var snapshot = Snapshot()
// Add the section
snapshot.appendSections([.main])
// Add the player array
snapshot.appendItems(clubs)
print(clubs.count)
// Tell the dataSource about the latest snapshot so it can update and animate.
dataSource.apply(snapshot, animatingDifferences: animatingDifferences)
}
func makeDataSource() -> DataSource {
let dataSource = DataSource(tableView: tableView) { (tableView, indexPath, club) -> UITableViewCell? in
let cell = tableView.dequeueReusableCell(withIdentifier: "ClubCell", for: indexPath)
let club = self.clubs[indexPath.row]
print("The name is \(club.name)")
cell.textLabel?.text = club.name
return cell
}
return dataSource
}
}

Answer 1

You need to apply a new snapshot to your table view once you have fetched the clubs. Your current subscriber simply assigns a value to clubs and nothing more.
You can use a sink subscriber to assign the new clubs value and then call applySnapshot. You need to ensure that this happens on the main queue, so you can use receive(on:).
self.subscriptions = [
self.viewModel.$clubs.receive(on: RunLoop.main).sink { clubs in
self.clubs = clubs
self.applySnapshot()
},
self.viewModel.$error.assign(to: \.errorMessage, on: self)
]