编辑：只需更改代码即可显示我对Singleton建议的尝试。
所以我试图创建一个应用程序，它将从UITableView中选择一个用户并将其传递给另一个UITableView。然后，它将附加到该视图中的数组并显示为新表。这个想法是用户可以从多个列表中进行选择，并创建一个由所有选择组成的列表。
但是，我对iOS开发非常陌生，虽然我可以让它取出所选值并在新的UITableView中显示它，但它只发送一个值而不保留或追加它。意思是我永远不会在列表中显示多个添加内容。
所以，我得到的是能够选择一个单元格，让我们说＆＃34;凯文史密斯＆＃34;，然后该值被发送到新的UITableView并显示给用户。但如果我去选择另一个值，约翰史密斯＆＃34;，那么只有John出现并且Kevin已经离开。
这是我的三个控制器：
第一个UITAbleView控制器
class PlayerViewController: UITableViewController {
var resultsController: NSFetchedResultsController<Player>!
let CDSPlayer = coreDataStackPlayer()
override func viewDidLoad() {
super.viewDidLoad()
tableView.allowsMultipleSelection = true
let request: NSFetchRequest<Player> = Player.fetchRequest()
let sortDescriptor = NSSortDescriptor(key: "level", ascending: true)
request.sortDescriptors = [sortDescriptor]
resultsController = NSFetchedResultsController(
fetchRequest: request,
managedObjectContext: CDSPlayer.managedContext,
sectionNameKeyPath: nil,
cacheName: nil
)
resultsController.delegate = self
do{
try resultsController.performFetch()
} catch {
print("Perform Fetch Error: \(error)")
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
// #warning Incomplete implementation, return the number of rows
return resultsController.sections?[section].numberOfObjects ?? 0
}
override func tableView(_ _tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell{
let cell = tableView.dequeueReusableCell(withIdentifier: "PlayerCell", for: indexPath)
let selectedIndexPaths = tableView.indexPathsForSelectedRows
let rowIsSelected = selectedIndexPaths != nil && selectedIndexPaths!.contains(indexPath)
cell.accessoryType = rowIsSelected ? .checkmark : .none
let player = resultsController.object(at: indexPath)
cell.textLabel?.text = player.name
return cell
}
override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
performSegue(withIdentifier: "player2form", sender: tableView.cellForRow(at: indexPath))
}
override func tableView(_ tableView: UITableView, trailingSwipeActionsConfigurationForRowAt indexPath: IndexPath) -> UISwipeActionsConfiguration? {
let action = UIContextualAction(style:.destructive, title: "Delete"){(action, view, completion) in
let player = self.resultsController.object(at: indexPath)
self.resultsController.managedObjectContext.delete(player)
do {
try self.resultsController.managedObjectContext.save()
self.errorMessage(message: "Player Character Deleted.");
completion(true)
} catch {
print("Delete Failed: \(error)")
self.errorMessage(message: "Failed to Delete Player Character.");
completion(false)
}
}
action.image = UIImage(named: "trash")
action.backgroundColor = .red
return UISwipeActionsConfiguration(actions: [action])
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?){
if let _ = sender as? UIBarButtonItem, let vc = segue.destination as? AddPlayerViewController{
vc.managedContext = resultsController.managedObjectContext
}
if let cell = sender as? UITableViewCell, let vc = segue.destination as? AddPlayerViewController{
vc.managedContext = resultsController.managedObjectContext
if let indexPath = tableView.indexPath(for: cell){
let player = resultsController.object(at: indexPath)
Service.shared.allPlayers.append(player)
vc.player = player
}
}
}
//Error Function
func errorMessage(message:String){
let alert = UIAlertController(title: "Alert", message: message, preferredStyle:UIAlertControllerStyle.alert);
let okAction = UIAlertAction(title:"Ok", style:UIAlertActionStyle.default, handler:nil);
alert.addAction(okAction);
self.present(alert, animated: true, completion:nil);
}
}
extension PlayerViewController: NSFetchedResultsControllerDelegate{
func controllerWillChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
tableView.beginUpdates()
}
func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
tableView.endUpdates()
}
func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange anObject: Any, at indexPath: IndexPath?, for type: NSFetchedResultsChangeType, newIndexPath: IndexPath?) {
switch type{
case .insert:
if let indexPath = newIndexPath{
tableView.insertRows(at: [indexPath], with: .automatic)
}
case .delete:
if let indexPath = indexPath{
tableView.deleteRows(at: [indexPath], with: .automatic)
}
case .update:
if let indexPath = indexPath, let cell = tableView.cellForRow(at: indexPath){
let player = resultsController.object(at: indexPath)
cell.textLabel?.text = player.name
}
default:
break
}
}
传递数据的选择视图：
class AddPlayerViewController: UIViewController {
var managedContext: NSManagedObjectContext!
var player: Player?
var selectedItems = [String]()
@IBOutlet weak var done_btn: UIButton!
@IBOutlet weak var playerInput: UITextField!
@IBOutlet weak var cancel_btn: UIButton!
@IBAction func add2combat(_ sender: UIButton) {
self.performSegue(withIdentifier: "player2combat", sender: self)
}
@IBAction func done(_ sender: UIButton) {
guard let name = playerInput.text, !name.isEmpty else {
return //Add notice user cannot save empty items
}
if let player = self.player {
player.name = name
} else {
//Set values from input to the cell
let player = Player(context: managedContext)
player.name = name
}
do {
try managedContext.save()
playerInput.resignFirstResponder()
dismiss(animated: true)
} catch {
print("Error Saving Player Character: \(error)")
}
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?){
if segue.identifier == "player2combat" {
let selectedItems : [String] = [playerInput.text!]
let otherVc = segue.destination as! CombatSceneViewController
otherVc.selectedItems = selectedItems
print(selectedItems)
}
}
@IBAction func cancel(_ sender: UIButton) {
playerInput.resignFirstResponder()
dismiss(animated: true)
}
override func viewDidLoad() {
super.viewDidLoad()
playerInput.becomeFirstResponder()
if let player = player {
playerInput.text = player.name
playerInput.text = player.name
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
获取数据并尝试将其附加到现有数组的UITableView。
class CombatSceneViewController: UITableViewController{
var selectedItems = Service.shared.allSelectedItems
override func viewDidLoad() {
super.viewDidLoad()
let otherVC = AddPlayerViewController()
selectedItems.append(contentsOf: otherVC.selectedItems)
saveData()
loadData()
print(selectedItems)
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return selectedItems.count
}
override func tableView(_ _tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell{
let cell = tableView.dequeueReusableCell(withIdentifier: "CombatCell", for: indexPath as IndexPath)
cell.textLabel?.text = selectedItems[indexPath.item]
return cell
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
tableView.reloadData()
}
func saveData() {
let data = NSMutableData()
// 1
let paths = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)
let path = paths[0]
let file = (path as NSString).appendingPathComponent("Persistent.plist")
//2
let archiver = NSKeyedArchiver(forWritingWith: data)
archiver.encode(selectedItems, forKey: "Agents")
archiver.finishEncoding()
data.write(toFile: file, atomically: true)
}
func loadData() {
let paths = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)
let path = paths[0]
let file = (path as NSString).appendingPathComponent("Persistent.plist")
// 1
if FileManager.default.fileExists(atPath: file) {
if let data = NSData(contentsOfFile: file) {
let unarchiver = NSKeyedUnarchiver(forReadingWith: data as Data)
selectedItems = unarchiver.decodeObject(forKey: "Agents") as! [String]
unarchiver.finishDecoding()
}
}
}
Singleton类：
class Service {
static let shared = Service()
var allPlayers = [Player]()
var allSelectedItems = [String]()
}
我希望我的格式正确...这是我在这里的第一篇文章，温柔的^^;。
答案 0 :(得分：0)
问题在于，当你回去时，旧玩家已经消失了，因为你没有保留它，你可以尝试为它创建一个单身
class Service {
static let shared = Service()
var allPlayers = [Player]()
var allSelectedItems = [String]()
}
//保持在这里
if let cell = sender as? UITableViewCell, let vc = segue.destination as? AddPlayerViewController{
vc.managedContext = resultsController.managedObjectContext
if let indexPath = tableView.indexPath(for: cell){
let player = resultsController.object(at: indexPath)
Service.shared.allPlayers.append(player) // add this line
vc.player = player
}
}
使用相同的逻辑来附加所选项目，当您到达final tableView时，使用
访问它们Service.shared.allPlayers
或者
Service.shared.selectedItems
这样你就可以为所有选中的玩家提供一个持久的容器。可在应用内部随处访问的项目