How to listen for data change with @Published variable then reload tableView-CodePudding

The most difficult task I face is to know the correct terminology to search for. I'm used to SwiftUI for an easy way to build an app in the fastest time possible. With this project I have to use UIKit and for this specific task.

Inside a view controller I created a tableView:

private let tableView: UITableView = {
    let table = UITableView()
    table.register(ProfileCell.self, forCellReuseIdentifier: ProfileCell.identifier)
    return table
}()

Later I reload the data inside viewDidLoad


override func viewDidLoad() {
    super.viewDidLoad()
    
    Task {
        do {
            try await viewModel.getProfiles()

            // Here I reload the table when data comes in
            self.tableView.reloadData()
        } catch {
            print(error)
        }
    }
    
    view.addSubview(tableView)
    tableView.delegate = self
    tableView.dataSource = self
}

So what is viewModel? In SwiftUI I'm used to having this inside a view struct:


@ObservedObject var viewModel = ProfilesViewModel()

..and that's what I have inside my view controller. I've searched for:

observedobject in uitableview
uitableview reload data on data change

..and more but noting useful for me to "pick up the pieces" with.

In same controller, I'm showMyViewControllerInACustomizedSheet which now uses UIHostingController:


private func showMyViewControllerInACustomizedSheet() {
    // A SwiftUI view along with viewModel being passed in
    let view = ProfilesMenu(viewModel: viewModel)
    let viewControllerToPresent = UIHostingController(rootView: view)
    if let sheet = viewControllerToPresent.sheetPresentationController {
        sheet.detents = [.medium(), .large()]
        sheet.largestUndimmedDetentIdentifier = .medium
        sheet.prefersScrollingExpandsWhenScrolledToEdge = false
        sheet.prefersEdgeAttachedInCompactHeight = true
        sheet.widthFollowsPreferredContentSizeWhenEdgeAttached = true
    }
    present(viewControllerToPresent, animated: true, completion: nil)
}

For the ProfilesViewModel:


class ProfilesViewModel: ObservableObject {

  // ProfilesResponse is omitted
  @Published var profiles = [ProfilesResponse]()

  public func getProfiles(endpoint: String? = nil) async throws -> Void {
    
   // After getting the data, I set the profiles variable
   self.profiles = [..]
  }
}

Whenever I call try await viewModel.getProfiles(endpoint: "..."), from ProfileMenu, I'd like to reload the tableView. What additional setup is required?

CodePudding user response：

In the comments, Vadian mentioned "Combine" where I did a Google search and found this. What works, for a basic demonstaration:


[..]
import Combine

class ViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {
  private let viewModel = ProfilesViewModel()
  private var cancellable: AnyCancellable?

  override func viewDidLoad() {
      super.viewDidLoad()
      
      Task {
          do {
              try await viewModel.getProfiles()

              // Remove this
              // self.tableView.reloadData()
          } catch {
              print(error)
          }


      }
      
      view.addSubview(tableView)
      tableView.delegate = self
      tableView.dataSource = self

      // Add this
      cancellable = viewModel.objectWillChange.sink(receiveValue: { [weak self] in
        self?.render()
      })
  }

  // Also add this
  private func render() {
    // TODO: Implement failures...
    DispatchQueue.main.async {
        self.tableView.reloadData()
    }
  }

  ...
}

objectWillChange was the key to my problem.