我试图在一个UIViewController中创建两个tableView。但是，当我尝试为UILabel分配值时，出现错误：致命错误：在展开可选值时意外发现nil
我想知道为什么，我有一个TableViewController与一个tableView几乎相同的代码，它没有任何问题。在尝试为其分配值时，看起来这些UI标签未初始化。但不明白如何解决它。
它在这里失败了：
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
var cell: UITableViewCell?
if tableView == self.guestsTableView {
let cell = tableView.dequeueReusableCell(withIdentifier: "guestCell", for: indexPath) as! GuestAtTableTableViewCell
if let guestsTable = guestsTableFetchedResultsController?.object(at: indexPath) {
print(guestsTable.guestName) // works fine, prints the value
print(cell.guestNameLabel.text) //fails here with error fatal error: unexpectedly found nil while unwrapping an Optional value
cell.guestNameLabel.text = guestsTable.guestName
cell.openTimeLabel.text = String(describing: guestsTable.openTime)
cell.cellDelegate = self
}
}
else if tableView == self.ordersTableView {
cell = tableView.dequeueReusableCell(withIdentifier: "orderCell", for: indexPath)
//to be done
}
// Configure the cell...
return cell!
}
此课程的完整代码：
import UIKit
import CoreData
class TableUIViewController: UIViewController, UITableViewDataSource, UITableViewDelegate, CellWithButtonDelegate {
//The following two variables will not be nil because prepare for segue will set them
var tableName: String?
var table: TablesTable? = nil
fileprivate var currentTableSession: TableSessionTable? {
get {
let tableSessionTable = TableSessionTable()
return tableSessionTable.getCurrentTableSession(table: table!)
}
}
fileprivate var guestsTableFetchedResultsController: NSFetchedResultsController<GuestsTable>?
fileprivate var ordersTableFetchedResultsController: NSFetchedResultsController<OrdersTable>?
@IBOutlet weak var tableNameLabel: UILabel!
@IBOutlet weak var tableCapacityLabel: UILabel!
@IBOutlet weak var tableCountOfGuestsLabel: UILabel!
@IBOutlet weak var tableDescriptionTextView: UITextView!
@IBAction func closeTableButtonPressed(_ sender: UIButton) {
}
@IBOutlet weak var guestsTableView: UITableView!
@IBOutlet weak var ordersTableView: UITableView!
@IBAction func addGuestButtonPressed(_ sender: UIButton) {
let guestsTable = GuestsTable()
let tablesTable = TablesTable()
let table = Table(tableName: tableName!, tableCapacity: 0, locationX: nil, locationY: nil, tableImage: nil)
try? guestsTable.addNewGuest(table: tablesTable.getOrCreateTable(table: table))
updateUI()
}
@IBAction func addOrderButtonPressed(_ sender: UIButton) {
}
override func viewDidLoad() {
guestsTableView.dataSource = self
guestsTableView.delegate = self
guestsTableView.register(GuestAtTableTableViewCell.self, forCellReuseIdentifier: "guestCell")
ordersTableView.dataSource = self
ordersTableView.delegate = self
ordersTableView.register(UITableViewCell.self, forCellReuseIdentifier: "orderCell")
updateUI()
}
func didPressButton(table: TablesTable) {
}
private func updateUI () {
let tableView = guestsTableView
let context = AppDelegate.viewContext
let request : NSFetchRequest<GuestsTable> = GuestsTable.fetchRequest()
request.predicate = NSPredicate(format: "table= %@", currentTableSession!)
request.sortDescriptors = [NSSortDescriptor(key: "guestName", ascending: true, selector: #selector(NSString.localizedCaseInsensitiveCompare(_:)))]
guestsTableFetchedResultsController = NSFetchedResultsController<GuestsTable>(fetchRequest: request, managedObjectContext: context, sectionNameKeyPath: nil, cacheName: nil)
try? guestsTableFetchedResultsController?.performFetch()
tableView?.reloadData()
}
private func updateUI1 () {
let tableView = ordersTableView
let context = AppDelegate.viewContext
let request : NSFetchRequest<OrdersTable> = OrdersTable.fetchRequest()
request.sortDescriptors = [NSSortDescriptor(key: "menuItem", ascending: true, selector: #selector(NSString.localizedCaseInsensitiveCompare(_:)))]
ordersTableFetchedResultsController = NSFetchedResultsController<OrdersTable>(fetchRequest: request, managedObjectContext: context, sectionNameKeyPath: nil, cacheName: nil)
try? ordersTableFetchedResultsController?.performFetch()
tableView?.reloadData()
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
var cell: UITableViewCell?
if tableView == self.guestsTableView {
let cell = tableView.dequeueReusableCell(withIdentifier: "guestCell", for: indexPath) as! GuestAtTableTableViewCell
if let guestsTable = guestsTableFetchedResultsController?.object(at: indexPath) {
print(guestsTable.guestName) // works fine, prints the value
print(cell.guestNameLabel.text) //fails here with error fatal error: unexpectedly found nil while unwrapping an Optional value
cell.guestNameLabel.text = guestsTable.guestName
cell.openTimeLabel.text = String(describing: guestsTable.openTime)
cell.cellDelegate = self
}
}
else if tableView == self.ordersTableView {
cell = tableView.dequeueReusableCell(withIdentifier: "orderCell", for: indexPath)
//to be done
}
// Configure the cell...
return cell!
}
func numberOfSections(in tableView: UITableView) -> Int {
if tableView == self.guestsTableView {
return guestsTableFetchedResultsController?.sections?.count ?? 1
}
else if tableView == self.ordersTableView {
return ordersTableFetchedResultsController?.sections?.count ?? 1
}
else {return 1}
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
if tableView == self.guestsTableView {
if let sections = guestsTableFetchedResultsController?.sections, sections.count > 0 {
return sections[section].numberOfObjects
}
else {
return 0
}
}
else if tableView == self.ordersTableView {
if let sections = ordersTableFetchedResultsController?.sections, sections.count > 0 {
return sections[section].numberOfObjects
}
else {
return 0
}
}
else {return 0}
}
func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
if tableView == self.guestsTableView {
if let sections = guestsTableFetchedResultsController?.sections, sections.count > 0 {
return sections[section].name
}
else {
return nil
}
}
else if tableView == self.ordersTableView {
if let sections = ordersTableFetchedResultsController?.sections, sections.count > 0 {
return sections[section].name
}
else {
return nil
}
}
else {return nil}
}
func sectionIndexTitles(for tableView: UITableView) -> [String]? {
if tableView == guestsTableView {
return guestsTableFetchedResultsController?.sectionIndexTitles
}
else {
return ordersTableFetchedResultsController?.sectionIndexTitles
}
}
func tableView(_ tableView: UITableView, sectionForSectionIndexTitle title: String, at index: Int) -> Int {
if tableView == guestsTableView {
return guestsTableFetchedResultsController?.section(forSectionIndexTitle: title, at: index) ?? 0
}
else if tableView == ordersTableView {
return ordersTableFetchedResultsController?.section(forSectionIndexTitle: title, at: index) ?? 0
}
else {return 0}
}
}
UITableViewCell类的完整代码：
import UIKit
class GuestAtTableTableViewCell: UITableViewCell {
weak var cellDelegate: CellWithButtonDelegate?
@IBOutlet weak var guestNameLabel: UILabel!
@IBOutlet weak var openTimeLabel: UILabel!
@IBAction func didPressButton(_ sender: UIButton) {
}
override func awakeFromNib() {
super.awakeFromNib()
// Initialization code
}
override func setSelected(_ selected: Bool, animated: Bool) {
super.setSelected(selected, animated: animated)
// Configure the view for the selected state
}
}
答案 0 :(得分：3)
我猜你的UITableViewCell的xib注册了xib而不是类。 使用以下内容：
guestsTableView.register(UINib.init(nibName: "GuestAtTableTableViewCell", bundle: nil), forCellReuseIdentifier: "guestCell")
由于您已在故事板中创建了原型单元格，因此您应该在故事板中选择单元格并在其中设置其标识符。接下来从guestCell的代码中删除注册行。它应该工作