Swift prepareForSegue對象是無

Question

我想將事件對象傳遞到DetailViewController，但它崩潰並說：「致命錯誤：意外地發現零，同時解開一個可選值」。我是積極的錯誤是在我的準備（賽格:)功能，但我已經在這個小時，我找不出如何解決它。任何幫助，將不勝感激。謝謝！

這裏是我的代碼：

class MainViewController: UIViewController, UITableViewDataSource, UITableViewDelegate { 

@IBOutlet weak var textView: UITextView! 
@IBOutlet weak var tableView: UITableView! 

var events = [Event]() 

override func viewDidLoad() { 
    super.viewDidLoad() 

    // Do any additional setup after loading the view. 


    tableView.delegate = self 
    tableView.dataSource = self 

    parseCSV() 
} 

override func didReceiveMemoryWarning() { 
    super.didReceiveMemoryWarning() 
    // Dispose of any resources that can be recreated. 
} 


@IBAction func logOutAction(sender: AnyObject) { 
    if FIRAuth.auth()?.currentUser != nil { 
     do { 
      try FIRAuth.auth()?.signOut() 
      let vc = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "SignUp") 
      present(vc, animated: true, completion: nil) 

     } catch let error as NSError { 
      print(error.localizedDescription) 
     } 
    } 
} 

func parseCSV() { 
    let path = Bundle.main.path(forResource: "eventData", ofType: "csv") 
    do { 
     let csv = try CSV(contentsOfURL: path!) 
     let rows = csv.rows 

     for row in rows { 
      let eventTitle = row["Title "]! 
      let eventLoc = row[" Location "]! 
      let eventStart = row[" Start_Time "]! 
      let eventEnd = row [" End_Time"]! 

      let event = Event(title: eventTitle, loc: eventLoc, start: eventStart, end: eventEnd) 
      events.append(event) 
     } 
    } catch let err as NSError { 
     print(err.debugDescription) 
    } 
} 


func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell { 
    if let cell = tableView.dequeueReusableCell(withIdentifier: "eventCell", for: indexPath) as? EventCell{ 
     let event = events[indexPath.row] 
     cell.updateUI(event: event) 

     return cell 
    } else { 
     return UITableViewCell() 
    } 
} 

func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int { 
    return events.count 
} 

func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) { 
    let event = events[indexPath.row] 
    performSegue(withIdentifier: "detailSegue", sender: event) 
} 

override func prepare(for segue: UIStoryboardSegue, sender: Any?) { 
    if segue.identifier == "detailSeque" { 
     if let detailVC = segue.destination as? DetailViewController { 
      if let event = sender as? Event { 
       detailVC.event = event 
      } 
     } 
    } 
} 
} 

我DetailViewController類：

class DetailViewController: UIViewController { 

var event: Event! 

@IBOutlet weak var eventTitle: UILabel! 

override func viewDidLoad() { 
    super.viewDidLoad() 

    eventTitle.text = event.title // error here. says event is nil. 
    } 
} 

Answer 1

由於SEGUE從你的連接，當你點擊的細胞，它已經自動執行。以編程方式執行它會導致你的segue執行兩次：一次值正確傳遞，一次沒有。

你可以改變你的SEGUE從視圖控制器，而不是在這種情況下，當前的代碼會工作，或更新您的代碼來完成所有的邏輯在prepareForSegue和刪除的didSelectRowAt您實現細胞連接：

override func prepare(for segue: UIStoryboardSegue, sender: Any?) { 
    if segue.identifier == "detailSeque" { 
     if let detailVC = segue.destination as? DetailViewController { 
      let row = tableView.indexPathForSelectedRow!.row 
      detailVC.event = events[row] 
     } 
    } 
}