Segue 以查看控制器崩溃

Posted 2023-03-12

【中文标题】Segue 以查看控制器崩溃

【英文标题】：Segue to view controller crashing

【发布时间】：2015-09-23 11:52:10

【问题描述】：

谁能告诉我我在这里做错了什么？我正在设计一个小应用程序，它正在从我的核心数据中添加、编辑和删除用户。但是，当我选择一行时，我的应用程序崩溃了，这应该将我带到下一个 viewController。 错误是：'致命错误：在展开可选值时意外发现 nil' 在此转换中为 segue 功能做准备失败了：让 contact:Contact = fetchedResultController.objectAtIndexPath(indexPath!) as！联系方式

所以当我点击一行时，它必须转到下一个视图控制器。

这是我的代码：

// 类 ContactsTableViewController

import UIKit
import CoreData

class ContactsTableViewController: UITableViewController, NSFetchedResultsControllerDelegate

    // MARK: - Properties
    let context = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext
    var fetchedResultController: NSFetchedResultsController = NSFetchedResultsController()


    // MARK: - Actions
    @IBAction func toggleMe(sender: AnyObject) 
        UberSideBar.toggleWindow()
    

    override func viewDidLoad() 
        super.viewDidLoad()

        fetchedResultController = getFtechedResultController()
        fetchedResultController.delegate = self
        fetchedResultController.performFetch(nil)
    

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

    // MARK: - Table view data source

    override func numberOfSectionsInTableView(tableView: UITableView) -> Int 
        let numberOfSection = fetchedResultController.sections?.count
        return numberOfSection!
    

    override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int 
        let numberOfinASection = fetchedResultController.sections?[section].numberOfObjects
        return numberOfinASection!
    

    // MARK: - Custom functions
    func getFtechedResultController() -> NSFetchedResultsController 
        fetchedResultController = NSFetchedResultsController(fetchRequest: taskFetchRequest(), managedObjectContext: context!, sectionNameKeyPath: nil, cacheName: nil)
        return fetchedResultController
    

    func taskFetchRequest() -> NSFetchRequest
        let fetchRequest = NSFetchRequest(entityName: "Contact")
        let sortDescriptor = NSSortDescriptor(key: "name", ascending: true)
        fetchRequest.sortDescriptors = [sortDescriptor]
        return fetchRequest
    

    func controllerDidChangeContent(controller: NSFetchedResultsController) 
        // Refresh tableview to fetch all data
        tableView.reloadData()
    

    override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell 
        let cell = tableView.dequeueReusableCellWithIdentifier("ContactCell", forIndexPath: indexPath) as! ContactcellTableViewCell
        let contact = fetchedResultController.objectAtIndexPath(indexPath) as! Contact
        println(contact.name)
        cell.nameLabel?.text = contact.name
        return cell
    

    override func tableView(tableView: UITableView, commitEditingStyle editingStyle: UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath) 
        let managedObject: NSManagedObject = fetchedResultController.objectAtIndexPath(indexPath) as! NSManagedObject
        context?.deleteObject(managedObject)
        context?.save(nil)
    

    override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) 
        performSegueWithIdentifier("editContact", sender: self)
    

    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) 
    if segue.identifier == "editContact" 

        let indexPath = tableView.indexPathForSelectedRow()
        let contactController: NewCategoryViewController = segue.destinationViewController as! NewCategoryViewController
        let contact:Contact = fetchedResultController.objectAtIndexPath(indexPath!) as! Contact
        contactController.contact = contact

    

和

   import UIKit
import CoreData


class NewCategoryViewController: UIViewController 

    // MARK: - Properties
    var contact: Contact? = nil

    // initialize the core data context:
    let context = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext

    // MARK: - Outlets
    @IBOutlet weak var imageHolder: UIImageView!
    @IBOutlet weak var nameField: UITextField!
    @IBOutlet weak var emailField: UITextField!
    @IBOutlet weak var phoneField: UITextField!
    @IBOutlet weak var categoryField: UITextField!

    // MARK: - Actions
    @IBAction func savebtn(sender: AnyObject) 

        let entity = NSEntityDescription.entityForName("Contact", inManagedObjectContext: context!)
        let newContact = Contact(entity: entity!, insertIntoManagedObjectContext: context)
            newContact.name = nameField.text
            newContact.email = emailField.text
            newContact.phone = phoneField.text
            //newContact.photo = UIImageJPEGRepresentation(imageHolder.image, 1)

        var error: NSError?

        context?.save(&error)

        if let errorSaving = error 
            var alert = UIAlertController(title: "Alert", message: "Couldn't save contact !!!", preferredStyle: UIAlertControllerStyle.Alert)
            alert.addAction(UIAlertAction(title: "Click", style: UIAlertActionStyle.Default, handler: nil))
            self.presentViewController(alert, animated: true, completion: nil)
         else 
            nameField.text = ""
            emailField.text = ""
            phoneField.text = ""
            var alert = UIAlertController(title: "Alert", message: "Contact added", preferredStyle: UIAlertControllerStyle.Alert)
            alert.addAction(UIAlertAction(title: "Ok", style: UIAlertActionStyle.Default, handler: nil))
            self.presentViewController(alert, animated: true, completion: nil)
        

    


    override func viewDidLoad() 
        super.viewDidLoad()

        if contact != nil 
            nameField.text = contact?.name
            emailField.text = contact?.email
            phoneField.text = contact?.phone

        
    

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

任何帮助将不胜感激

【问题讨论】：

显然sender不是cell对象，它是tableview控制器对象

【参考方案1】：

您不能将 prepareForSegue 中的发件人转换为 ContactcellTableViewCell，因为它是 ContactsTableViewController 类型。

不要做你正在做的事情，为了获得indexPath，只需做

let indexPath = tableView.indexPathForSelectedRow()

并删除这一行：

let cell = sender as! ContactcellTableViewCell

【讨论】：

它崩溃了吗？如果它确实有什么例外？它在哪里？

我试过这个： override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) if segue.identifier == "editContact" let indexPath = tableView.indexPathForSelectedRow()?.row let contactController: NewCategoryViewController = segue.destinationViewController 为！ NewCategoryViewController 让contact:Contact = fetchedResultController.objectAtIndexPath(indexPath!) as！联系 contactController.contact = contact 但我收到此错误 NSNumber is not a subtype of NSIndexPath

在这里崩溃：让contact:Contact = fetchedResultController.objectAtIndexPath(indexPath!) as！联系方式

你不能做 indexPath = tableView.indexPathForSelectedRow()?.row.

如果我这样做 let indexPath = tableView.indexPathForSelectedRow()，那么这里就崩溃了 let contact:Contact = fetchedResultController.objectAtIndexPath(indexPath!) as！接触到以下错误：致命错误：unwrapping an Optional value 时意外发现 nil