Swift Xcode 13 Programmatic UITableViewController nil delegate - ios

Question

The Delegated function fires but crashes as its nil, the objects in the items array is populated by CoreData, this var model: CoreDataModel = CoreDataModel(CoreDataController.shared) has to be instantiated rather than as expected in the viewDidLoad to prevent a nil error for the table view row count (model.items.count)
On startup the items array is the complete Sqlite DB, on search its the subset of the table and printing to the console proves the array is changed and only has the subset of Albums.
BaseViewController
import UIKit
import CoreData
protocol UITableViewDataSource {
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath)
}
protocol MasterModel {
var client: LastFMClient { get }
func searchFeed(with userSearchTerm: String?, completion: #escaping (Bool) -> Void)
}
protocol DataReloadTableViewDelegate: class {
func reloadAlbumsTable()
}
class BaseViewController: UITableViewController, MasterModel {
let cellId = "sdlfjowieurewfn3489844224947824dslaksjfs;ad"
let logoContainer = UIView(frame: CGRect(x: 0, y: 0, width: 44, height: 44))
let imageView = UIImageView(frame: CGRect(x: 0, y: 0, width: 44, height: 44))
let image = UIImage(named: "lastFMRedBlack")
let searchBar = UISearchBar()
let client = LastFMClient()
var model: CoreDataModel = CoreDataModel(CoreDataController.shared)
private var searchResults: Root?
override func viewDidLoad() {
super.viewDidLoad()
setupSearchController()
tableView.register(UITableViewCell.self, forCellReuseIdentifier: cellId)
tableView.register(SubtitleTableViewCell.self, forCellReuseIdentifier: cellId)
tableView.tableFooterView = UIView(frame: CGRect.zero)
tableView.separatorColor = UIColor(red: 72.5/255, green: 0/255, blue: 0/255, alpha: 1)
imageView.contentMode = .scaleAspectFit
imageView.image = image
logoContainer.addSubview(imageView)
navigationItem.titleView = logoContainer
print(FileManager.default.urls(for: .documentDirectory, in: .userDomainMask))
model.delegate = self
model.fetchAllAlbums()
}
// MARK - SearchBar
private func setupSearchController() {
searchBar.sizeToFit()
searchBar.placeholder = "Search for Album"
searchBar.delegate = self
showSearchBarButton(shouldShow: true)
}
func showSearchBarButton (shouldShow: Bool) {
if shouldShow {
navigationItem.rightBarButtonItem = UIBarButtonItem(barButtonSystemItem: .search, target: self, action: #selector(handleShowSearchBar))
} else {
searchBar.showsCancelButton = true
navigationItem.rightBarButtonItem = nil
}
}
func search(shouldShow: Bool) {
showSearchBarButton(shouldShow: !shouldShow)
navigationItem.titleView = shouldShow ? searchBar : logoContainer
}
#objc func handleShowSearchBar(){
search(shouldShow: true)
searchBar.becomeFirstResponder()
}
// MARK - API Request
func searchFeed(with userSearchTerm: String?, completion: #escaping (Bool) -> Void) {
// Use the API to get data
client.getFeed(from: LastFMRequest.albumSearch(userSearchTerm: userSearchTerm) ) { result in
switch result {
case .success(let data):
do {
let data = try DataParser.parse(data, type: RootNode.self)
self.searchResults = data.results
completion(true)
} catch {
print(error.localizedDescription)
completion(false)
}
case .failure(let error):
print(error.localizedDescription)
completion(false)
}
}
}
}
extension BaseViewController: UISearchBarDelegate {
func searchBarTextDidEndEditing(_ searchBar: UISearchBar) {
searchBar.text = nil
}
func searchBarCancelButtonClicked(_ searchBar: UISearchBar) {
search(shouldShow: false)
}
func searchBarSearchButtonClicked(_ searchBar: UISearchBar) {
guard let searchTextString = searchBar.text else { return }
searchFeed(with: searchTextString.replacingOccurrences(of: " ", with: "+").lowercased(), completion: {_ in
if self.searchResults!.albumMatches.album.count == 0 {
DispatchQueue.main.async {
let alertController = UIAlertController(title: "No Albums Found", message: "Try Another Keyword(s)", preferredStyle: .alert)
let OKAction = UIAlertAction(title: "OK", style: .default) { action in
print("Pressed OK")
}
alertController.addAction(OKAction)
self.present(alertController, animated: true, completion: nil)
}
} else {
let dataManager = DataManager(data: self.searchResults!)
do {
try dataManager.saveData()
} catch {
print(error)
}
}
})
search(shouldShow: false)
searchBar.resignFirstResponder()
}
}
class SubtitleTableViewCell: UITableViewCell {
override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
super.init(style: .subtitle, reuseIdentifier: reuseIdentifier)
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
}
extension BaseViewController: UITableViewDataSource {
var numberOrSections: Int { return 1 }
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
guard section >= 0 && section < numberOrSections else { return 0 }
return model.items.count
}
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: cellId, for: indexPath)
let albumItem = model.items[indexPath.row]
cell.textLabel?.text = albumItem.value(forKeyPath: "name") as? String
cell.detailTextLabel?.text = albumItem.value(forKeyPath: "artist") as? String
cell.accessoryType = .disclosureIndicator
// Populate the cell from the object
return cell
}
override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
let vc = DetailViewController()
let albumItem = model.items[indexPath.row]
vc.iamgeURL = albumItem.value(forKeyPath: "imageUrl") as? String
vc.albumName = albumItem.value(forKeyPath: "name") as? String
navigationController?.pushViewController(vc, animated: true)
}
}
extension BaseViewController: DataReloadTableViewDelegate {
func reloadAlbumsTable(){
DispatchQueue.main.async {
print(self.model.items.count)
self.tableView.reloadData()
}
}
}
CoreDataModel
import Foundation
import CoreData
class CoreDataModel {
weak var delegate: DataReloadTableViewDelegate?
let coreDataController: CoreDataController
var items:[Albums] = []
init(_ coreDataController: CoreDataController) {
self.coreDataController = coreDataController
self.coreDataController.mainContext.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy
}
internal func saveSearchAlbums(responseData: Root) throws {
let newSearch = Searches(context: coreDataController.mainContext)
newSearch.searchQuery = responseData.attr.forField
for (_, element) in responseData.albumMatches.album.enumerated() {
let newAlbum = Albums(context: coreDataController.mainContext)
let artistName = element.artist
let albumName = element.name
let imageUrlTwo = element.image[2].text
let imageUrlZero = element.image[0].text
let imageUrlOne = element.image[1].text
var imageUrl: String = ""
if !JustLetters.blank(text: imageUrlTwo) {
imageUrl = imageUrlTwo
}
if !JustLetters.blank(text: imageUrlZero) {
imageUrl = imageUrlZero
}
if !JustLetters.blank(text: imageUrlOne) {
imageUrl = imageUrlOne
}
if !JustLetters.blank(text: artistName) && !JustLetters.blank(text: albumName) && !JustLetters.blank(text: imageUrl) {
newAlbum.searches = newSearch
newAlbum.artist = artistName
newAlbum.name = albumName
newAlbum.imageUrl = imageUrl
newSearch.addToAlbums(newAlbum)
}
}
// Save context
coreDataController.saveContext()
fetchAlbumsByKeyword(searchTerm: responseData.attr.forField)
}
internal func fetchAlbumsByKeyword(searchTerm: String) {
// Create Fetch Request
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "Albums")
// Add Sort Descriptor
let sortDescriptor = NSSortDescriptor(key: "name", ascending: true)
fetchRequest.sortDescriptors = [sortDescriptor]
// Add Predicate
let predicate = NSPredicate(format: "name CONTAINS[c] %#", searchTerm)
fetchRequest.predicate = predicate
do {
items = try coreDataController.mainContext.fetch(fetchRequest) as! [Albums]
} catch {
print(error)
}
delegate!.reloadAlbumsTable()
}
internal func fetchAllAlbums() {
// Create the FetchRequest for all searches
let allAlbums: NSFetchRequest = Albums.fetchRequest()
do {
items = try coreDataController.mainContext.fetch(allAlbums)
} catch {
print(error)
}
}
}

Answer 1

Delegate is assigned/set on the class name and not on any instance identifier so a delegate can only be set on a class with one instance
I am unable to show specific proof, I rely on cause and effect of a single change to make the above statement.
I had more than one instance of CoreDataModel, I set the delegate on the first instance in the viewDidLoad, the second instance is set on the search click. I refactored out the DataManager Class which itself creates and instance of CoreDataModel.
The final result is the delegate is not nil and performs as expected. Repo 'show_album_search_results' branch