斯威夫特火力地堡持久

Question

我试图使火力地堡的持久性，但我的代码保持与崩溃：

类型的未捕获的异常NSException

我已经试过我的viewDidLoad下的代码行终止以及在DataService下，但我仍然遇到同样的崩溃。什么做我需要做来解决这个问题，我面对

import UIKit 
import Firebase 

class HomeTeamSelectionVC: UIViewController, UITableViewDataSource, UITableViewDelegate { 

    @IBOutlet weak var tableView: UITableView! 

    var club: Clubs! 
    var player = [Players]() 
    var playerFirstName = String() 
    var playerLastName = String() 
    var playerSelected: Bool = false 


    override func viewDidLoad() { 
     super.viewDidLoad() 

     FIRDatabase.database().persistenceEnabled = true //Correct use of???? 

     CLUB_KEY = "" 
     CLUB_KEY = club.clubKey 

     tableView.dataSource = self 
     tableView.delegate = self 


     DataService.ds.REF_PLAYERS.queryOrdered(byChild: "clubKey").queryEqual(toValue: club.clubKey).observe(.value, with: { (snapshot) in 

      print("PLAYERS_COUNT: \(snapshot.childrenCount)") 
      print("PLAYERS_SNAPSHOT: \(snapshot)") 

      self.player = [] 
      if let snapshots = snapshot.children.allObjects as? [FIRDataSnapshot] { 

       for snap in snapshots { 
        if let playerDict = snap.value as? Dictionary<String, AnyObject> { 
         let key = snap.key 

         let players = Players(playerKey: key, dictionary: playerDict) 
         self.player.append(players) 

        } 
       } 
      } 
      //   self.tableView.reloadData() 
     }) { (error) in 
      print(error.localizedDescription) 
      print("CHET: local error") 
     } 
    } 

    func numberOfSections(in tableView: UITableView) -> Int { 

     return 1 
    } 

    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int { 

     return player.count 
    } 

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell { 

     let players = player[indexPath.row] 
     if let cell = tableView.dequeueReusableCell(withIdentifier: "HomeTeamPlayersCell") as? HomeTeamPlayersCell { 
      cell.configureCell(players) 
      return cell 
     } else { 
      return HomeTeamPlayersCell() 
     } 
    } 

    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) { 

     let players: Players! 
     players = player[indexPath.row] 

     print (players.playerKey) 
     print (players.playerFirstName) 
     print (players.playerLastName) 

     dismiss(animated: true, completion: nil) 
    } 
} 

Answer 1

从Firebase documentation for persistenceEnabled property：

注意，这个属性必须创建第一个数据库引用前设置，只需要调用一次每个应用。

因此，标准的做法是将其设置一次在AppDelegate类。例如：

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool { 
    FIRApp.configure() 
    FIRDatabase.database().persistenceEnabled = true 
    ... 
    return true 

}