iOS - 无法从其dataSource获取单元格
我编写了一个swift文件来控制两个用户之间的消息传递连接。由于某种原因，文件在加载时崩溃并返回此错误：
import UIKit
class chatViewController: UIViewController {
@IBOutlet weak var tableView: UITableView!
var timer = NSTimer()
var tableBackgroundInc = 1
let EnigmaMachine = EncryptionMachine()
var friendChosen: String!
var isConnectedToInternet: Bool!
var receivedUsername:String!
@IBOutlet weak var testLabel: UILabel!
var messageStringRecords = []
var messages: NSMutableArray = NSMutableArray()
func sendAlert(subject: String, message: String) {
let alertController = UIAlertController(title: subject, message:
message, preferredStyle: UIAlertControllerStyle.Alert)
alertController.addAction(UIAlertAction(title: "Dismiss", style: UIAlertActionStyle.Default,handler: nil))
self.presentViewController(alertController, animated: true, completion: nil)
}
func tableView(tableView: UITableView, numberOfRowsInSection Section: Int) -> Int {
return self.messages.count
}
/*@IBAction func refreshButton(sender: UIButton) {
reloadTable()
}*/
@IBOutlet weak var messageTextInput: UITextField!
@IBAction func sendButton(sender: UIButton) {
let chatPartner = self.friendChosen
let username = NSUserDefaults.standardUserDefaults().stringForKey("username")! as String
let theMessage = messageTextInput.text! as String
let messageTextPreOne = EnigmaMachine.encrypt(theMessage)
let messageTextPreTwo = messageTextPreOne.stringByReplacingOccurrencesOfString(" ", withString: "039254space925403")
let messageText = self.voidInvalidCharacters(messageTextPreTwo)
if messageText != "" {
let secretKey = "0000"
let myUrl = NSURL(string: "http://www.neverforgottenbbq.com/gfg/sendMessage.php")
let request = NSMutableURLRequest(URL: myUrl!)
request.HTTPMethod = "POST"
let postString = "secretKey=\(secretKey)&username=\(username)&chatPartner=\(chatPartner)&message=\(messageText)"
request.HTTPBody = postString.dataUsingEncoding(NSUTF8StringEncoding)
let task = NSURLSession.sharedSession().dataTaskWithRequest(request) {
data, response, error in
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0)) {
if let responseData = data {
let responseString = NSString(data: responseData, encoding: NSUTF8StringEncoding)
if error != nil {
print("Error: \(error)")
}
dispatch_async(dispatch_get_main_queue()) {
print("")
}
} else {
print("The connection quit")
}
}
}
task.resume()
}
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = self.tableView.dequeueReusableCellWithIdentifier("cell", forIndexPath: indexPath) as! chatTableViewCell
//cell.messageLabel?.text = self.messages.objectAtIndex(indexPath.row) as? String
let wholeMessage = self.messages.objectAtIndex(indexPath.row) as? String
if wholeMessage! as String != "Loading......" && wholeMessage! as String != "No messages" {
let splitMessage = wholeMessage!.componentsSeparatedByString("203598123589")
let theMessage = splitMessage[0]
if EnigmaMachine.decrypt(splitMessage[1]) as String == friendChosen.uppercaseString as String {
let completeMessage = friendChosen.uppercaseString + ": " + theMessage
cell.messageLabel?.text = completeMessage
} else {
cell.messageLabel.textAlignment = NSTextAlignment.Right
let completeMessage = theMessage
cell.messageLabel?.text = completeMessage
}
} else {
cell.messageLabel?.text = wholeMessage! as String
}
tableView.estimatedRowHeight = requiredHeight(self.messages.objectAtIndex(indexPath.row) as! String)
tableView.rowHeight = UITableViewAutomaticDimension
cell.layer.cornerRadius = 5
cell.layer.masksToBounds = true
return cell
}
func requiredHeight(text:String) -> CGFloat {
let font = UIFont(name: "Georgia", size: 16.0)
let label:UILabel = UILabel(frame: CGRectMake(0, 0, 200, CGFloat.max))
label.numberOfLines = 0
label.lineBreakMode = NSLineBreakMode.ByWordWrapping
label.font = font
label.text = text
label.sizeToFit()
return label.frame.height
}
func reloadTable() {
refreshTable()
self.messages = []
let chatPartner = NSUserDefaults.standardUserDefaults().stringForKey("usernameToMessageWith")! as String
let username = NSUserDefaults.standardUserDefaults().stringForKey("username")! as String
let myUrl = NSURL(string: "http://www.neverforgottenbbq.com/gfg/getMessagesForCurrentChat.php")
let request = NSMutableURLRequest(URL: myUrl!)
request.HTTPMethod = "POST"
let postString = "username=\(username)&chatPartner=\(chatPartner)"
request.HTTPBody = postString.dataUsingEncoding(NSUTF8StringEncoding)
let task = NSURLSession.sharedSession().dataTaskWithRequest(request) {
data, response, error in
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0)) {
if let responseData = data {
let responseString = NSString(data: responseData, encoding: NSUTF8StringEncoding)
if error != nil {
print("Error: \(error)")
}
dispatch_async(dispatch_get_main_queue()) {
self.messageStringRecords = responseString!.componentsSeparatedByString("3292985383")
for index in self.messageStringRecords {
let indexSplit = index.componentsSeparatedByString("9254203598")
if indexSplit.count > 1 {
let theMessage = indexSplit[0]
let messageId = indexSplit[1]
self.updateReadStatus(messageId)
let theNewMessage = theMessage
self.messages.addObject(self.EnigmaMachine.decrypt(theNewMessage))
self.tableBackgroundInc = 1
self.tableView.reloadData()
}
}
}
} else {
print("The connection quit")
}
}
}
task.resume()
self.tableView.estimatedRowHeight = 44.0
self.tableView.rowHeight = UITableViewAutomaticDimension
self.tableBackgroundInc = 1
self.tableView.reloadData()
}
}
func updateReadStatus(messageId: String) {
let theSecretKey = "0000"
let myUrl = NSURL(string: "http://www.neverforgottenbbq.com/gfg/updateReadStatus.php")
let request = NSMutableURLRequest(URL: myUrl!)
request.HTTPMethod = "POST"
let postString = "id=\(messageId)&secretKey=\(theSecretKey)"
request.HTTPBody = postString.dataUsingEncoding(NSUTF8StringEncoding)
let task = NSURLSession.sharedSession().dataTaskWithRequest(request) {
data, response, error in
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0)) {
if let responseData = data {
_ = NSString(data: responseData, encoding: NSUTF8StringEncoding)
if error != nil {
print("Error: \(error)")
}
dispatch_async(dispatch_get_main_queue()) {
print("")
}
} else {
print("The connection quit")
}
}
}
task.resume()
}
func voidInvalidCharacters(stringToVoid: String) -> String {
var returnString = ""
var sanitizedArray: [String] = []
let acceptableCharacters = [
"A",
"B",
"C",
"D",
"E",
"F",
"G",
"H",
"I",
"J",
"K",
"L",
"M",
"N",
"O",
"P",
"Q",
"R",
"S",
"T",
"U",
"V",
"W",
"X",
"Y",
"Z",
"a",
"b",
"c",
"d",
"e",
"f",
"g",
"h",
"i",
"j",
"k",
"l",
"m",
"n",
"o",
"p",
"q",
"r",
"s",
"t",
"u",
"v",
"w",
"x",
"y",
"z",
"0",
"1",
"2",
"3",
"4",
"5",
"6",
"7",
"8",
"9",
"-",
".",
"_",
"~",
":",
"/",
"?",
"#",
"[",
"]",
"@",
"!",
"$",
"'",
"(",
")",
"*",
"+",
",",
";",
"="
]
let stringToVoidArray = Array(stringToVoid.characters)
for letter in stringToVoidArray {
var isAcceptable = false
for character in acceptableCharacters {
if character as String == String(letter) {
isAcceptable = true
}
}
if isAcceptable == true {
sanitizedArray.append(String(letter))
}
}
for letter in sanitizedArray {
returnString = returnString + letter
}
return returnString
}
func keyboardWillShow(notification: NSNotification) {
if let keyboardSize = (notification.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.CGRectValue() {
self.view.frame.origin.y -= keyboardSize.height
}
}
func keyboardWillHide(notification: NSNotification) {
if let keyboardSize = (notification.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.CGRectValue() {
self.view.frame.origin.y += keyboardSize.height
}
}
func dismissKeyboard() {
self.messageTextInput.resignFirstResponder()
}
func refreshTable () {
let newMessages: NSMutableArray = NSMutableArray()
let chatPartner = self.receivedUsername
if chatPartner == "" {
self.sendAlert("Error", message: "Can not connect to chat partner")
}
let username = NSUserDefaults.standardUserDefaults().stringForKey("username")! as String
let myUrl = NSURL(string: "http://www.neverforgottenbbq.com/gfg/getMessagesForCurrentChat.php")
let request = NSMutableURLRequest(URL: myUrl!)
request.HTTPMethod = "POST"
let postString = "username=\(username)&chatPartner=\(chatPartner)"
request.HTTPBody = postString.dataUsingEncoding(NSUTF8StringEncoding)
let task = NSURLSession.sharedSession().dataTaskWithRequest(request) {
data, response, error in
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0)) {
let responseString = NSString(data: data!, encoding: NSUTF8StringEncoding)
if error != nil {
print("Error: \(error)")
}
dispatch_async(dispatch_get_main_queue()) {
if responseString !== "" {
self.messageStringRecords = responseString!.componentsSeparatedByString("3292985383")
for index in self.messageStringRecords {
let indexSplit = index.componentsSeparatedByString("9254203598")
let theMessage = indexSplit[0]
let theNewMessagePre = theMessage.stringByReplacingOccurrencesOfString("039254space925403", withString: " ")
let theNewMessage = theNewMessagePre + "203598123589\(String(indexSplit[3]))"
newMessages.addObject(self.EnigmaMachine.decrypt(theNewMessage))
}
self.messages = []
for i in newMessages {
self.messages.addObject(i)
}
self.tableBackgroundInc = 1
self.tableView.reloadData()
} else {
self.messages = []
self.messages.addObject("No messages")
self.tableView.reloadData()
}
}
}
}
task.resume()
}
override func viewDidLoad() {
super.viewDidLoad()
NSNotificationCenter.defaultCenter().addObserverForName(
UIApplicationUserDidTakeScreenshotNotification,
object: nil,
queue: NSOperationQueue.mainQueue())
{
notification in
2
let chatPartner = self.friendChosen
let username = NSUserDefaults.standardUserDefaults().stringForKey("username")! as String
let theMessage = "I took a screenshot. I am sorry that I cannot be trusted :("
let messageTextPreOne = self.EnigmaMachine.encrypt(theMessage)
let messageTextPreTwo = messageTextPreOne.stringByReplacingOccurrencesOfString(" ", withString: "039254space925403")
let messageText = self.voidInvalidCharacters(messageTextPreTwo)
if messageText != "" {
let secretKey = "00000"
let myUrl = NSURL(string: "http://www.neverforgottenbbq.com/gfg/sendMessage.php")
let request = NSMutableURLRequest(URL: myUrl!)
request.HTTPMethod = "POST"
let postString = "secretKey=\(secretKey)&username=\(username)&chatPartner=\(chatPartner)&message=\(messageText)"
request.HTTPBody = postString.dataUsingEncoding(NSUTF8StringEncoding)
let task = NSURLSession.sharedSession().dataTaskWithRequest(request) {
data, response, error in
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0)) {
_ = NSString(data: data!, encoding: NSUTF8StringEncoding) // lazy responseString: NSString
if error != nil {
print("Error: \(error)")
}
dispatch_async(dispatch_get_main_queue()) {
//print(responseString)
}
}
}
task.resume()
} else {
self.sendAlert("Error", message: "You cannot send a blank message")
}
}
self.receivedUsername = friendChosen
self.tableView.separatorStyle = UITableViewCellSeparatorStyle.None
let swipe: UISwipeGestureRecognizer = UISwipeGestureRecognizer(target: self, action: "dismissKeyboard")
swipe.direction = UISwipeGestureRecognizerDirection.Down
self.view.addGestureRecognizer(swipe)
NSNotificationCenter.defaultCenter().addObserver(self, selector: Selector("keyboardWillShow:"), name: UIKeyboardWillShowNotification, object: nil)
NSNotificationCenter.defaultCenter().addObserver(self, selector: Selector("keyboardWillHide:"), name: UIKeyboardWillHideNotification, object: nil)
self.messages.addObject("Loading......")
refreshTable()
print("this is a test")
}
override func viewDidAppear(animated: Bool) {
super.viewDidAppear(animated)
timer = NSTimer.scheduledTimerWithTimeInterval(2, target: self, selector: Selector("refreshTable"), userInfo: nil, repeats: true)
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject!) {
timer.invalidate()
}
}
我不小心删除了该文件。幸运的是我有一个备份，所以我能够以相同的名称创建一个新文件，并将所有代码粘贴到其中。
有问题的代码：
{{1}}
非常感谢您的帮助，
尼克
5 个答案:
答案 0 :(得分：16)
我自己也对此有所了解并将其弄清楚...... chatViewController未标记为实施UITableViewDataSource协议。
这是Swift 3的新行为。
更改行：
class chatViewController: UIViewController {
为：
class chatViewController: UIViewController, UITableViewDataSource {
代码可以运行。
答案 1 :(得分：4)
错误实质上是说它无法为表视图获取单元格。这意味着您将从nil返回cellForRowAtIndexPath。
但是你有这样一个方法，并且写了它不能返回nil。问题是您的cellForRowAtIndexPath函数嵌入在另一个函数中。它不可能。确保所有表视图数据源和委托函数都是类中的顶级函数。
答案 2 :(得分：4)
Swift 3.0
您只需添加 UITableViewDelegate 和 UITableViewDataSource
import UIKit
class ViewController: UIViewController, UITableViewDelegate, UITableViewDataSource
下图仅供参考。
答案 3 :(得分：3)
如果您没有为可重复使用的单元格指定标识符，但是您尝试在类中引用它，则会发生这种不常见的错误。
// Set the cell to be the custom cell
let cell : CustomCell! = tableView.dequeueReusableCellWithIdentifier("cell") as? CustomCell
答案 4 :(得分：1)
这是Xcode 8.0中的变化
class chatViewController：UIViewController {
将此行更改为此
class chatViewController：UIViewController，UITableViewDataSource，UITableViewDelegate {
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