Swift PrepareForsegue对象是零

Question

我正在尝试将事件对象传递到详细信息视图controller中，但它崩溃并说："致命错误：意外地发现了无需可选的值时找到了无效"。我很肯定的是，我准备的错误（用于segual :)功能，但是我已经使用了几个小时了，我找不到解决方法。任何帮助，将不胜感激。谢谢！

这是我的代码：

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
            }
        }
    }
}
}

我的详细信息ViewController类：

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

由于SEGUE从您的单元格连接，因此在点击单元格时已经自动执行。通过编程执行它，导致您的segue执行两次：一旦正确传递，并且一次没有。

。

您可以更改您的segue以从视图控制器而不是单元格连接，在这种情况下，当前代码将起作用，或更新代码以执行prepareForSegue中的所有逻辑，然后删除您对didSelectRowAt的实现：

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]
        }
    }
}