单击表格单元格

Question

我下载了一个完美运行的演示聊天应用程序但是当我将它实现到我自己的应用程序时，它会崩溃并且代码完全相同。该应用程序使您能够创建聊天室，我的应用程序到此为止，但当您单击现在出现在桌面上的聊天室名称时，我收到以下错误：

  

断言失败 - [Irish_League_Grounds.ChatViewController viewWillAppear：]，/ Users / ryanball / Desktop / Irish League   理由/荚/ JSQMessagesViewController / JSQMessagesViewController /控制器/ JSQMessagesViewController.m：277   2017-05-17 17：32：55.815 Irish League Grounds [20456：681491]

     

由于未捕获的异常而终止应用   'NSInternalInconsistencyException'，原因：'参数无效   满足：self.senderDisplayName！= nil'

这是我在两个视图控制器之间的代码：

import UIKit
import Firebase

enum Section: Int {
  case createNewChannelSection = 0
  case currentChannelsSection
}

class ChannelListViewController: UITableViewController {

  // MARK: Properties
  var senderDisplayName: String?
  var newChannelTextField: UITextField?

  private var channelRefHandle: FIRDatabaseHandle?
  private var channels: [Channel] = []

  private lazy var channelRef: FIRDatabaseReference = FIRDatabase.database().reference().child("channels")

  // MARK: View Lifecycle

  override func viewDidLoad() {
    super.viewDidLoad()
    title = "RW RIC"
    observeChannels()
  }

  deinit {
    if let refHandle = channelRefHandle {
      channelRef.removeObserver(withHandle: refHandle)
    }
  }

  // MARK :Actions

  @IBAction func createChannel(_ sender: AnyObject) {
    if let name = newChannelTextField?.text {
      let newChannelRef = channelRef.childByAutoId()
      let channelItem = [
        "name": name
      ]
      newChannelRef.setValue(channelItem)
    }    
  }

  // MARK: Firebase related methods

  private func observeChannels() {
    // We can use the observe method to listen for new
    // channels being written to the Firebase DB
    channelRefHandle = channelRef.observe(.childAdded, with: { (snapshot) -> Void in
      let channelData = snapshot.value as! Dictionary<String, AnyObject>
      let id = snapshot.key
      if let name = channelData["name"] as! String!, name.characters.count > 0 {
        self.channels.append(Channel(id: id, name: name))
        self.tableView.reloadData()
      } else {
        print("Error! Could not decode channel data")
      }
    })
  }

  // MARK: Navigation

  override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    super.prepare(for: segue, sender: sender)

    if let channel = sender as? Channel {
      let chatVc = segue.destination as! ChatViewController

      chatVc.senderDisplayName = senderDisplayName
      chatVc.channel = channel
      chatVc.channelRef = channelRef.child(channel.id)
    }
  }

  // MARK: UITableViewDataSource

  override func numberOfSections(in tableView: UITableView) -> Int {
    return 2
  }

  override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    if let currentSection: Section = Section(rawValue: section) {
      switch currentSection {
      case .createNewChannelSection:
        return 1
      case .currentChannelsSection:
        return channels.count
      }
    } else {
      return 0
    }
  }

  override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let reuseIdentifier = (indexPath as NSIndexPath).section == Section.createNewChannelSection.rawValue ? "NewChannel" : "ExistingChannel"
    let cell = tableView.dequeueReusableCell(withIdentifier: reuseIdentifier, for: indexPath)

    if (indexPath as NSIndexPath).section == Section.createNewChannelSection.rawValue {
      if let createNewChannelCell = cell as? CreateChannelCell {
        newChannelTextField = createNewChannelCell.newChannelNameField
      }
    } else if (indexPath as NSIndexPath).section == Section.currentChannelsSection.rawValue {
      cell.textLabel?.text = channels[(indexPath as NSIndexPath).row].name
    }

    return cell
  }

  // MARK: UITableViewDelegate

  override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    if (indexPath as NSIndexPath).section == Section.currentChannelsSection.rawValue {
      let channel = channels[(indexPath as NSIndexPath).row]
      self.performSegue(withIdentifier: "ShowChannel", sender: channel)
    }
  }

}

这是第二个视图控制器：

import UIKit
import Photos
import Firebase
import JSQMessagesViewController

final class ChatViewController: JSQMessagesViewController {

  // MARK: Properties
  private let imageURLNotSetKey = "NOTSET"

  var channelRef: FIRDatabaseReference?

  private lazy var messageRef: FIRDatabaseReference = self.channelRef!.child("messages")
  fileprivate lazy var storageRef: FIRStorageReference = FIRStorage.storage().reference(forURL: "gs://chatchat-871d0.appspot.com")
  private lazy var userIsTypingRef: FIRDatabaseReference = self.channelRef!.child("typingIndicator").child(self.senderId)
  private lazy var usersTypingQuery: FIRDatabaseQuery = self.channelRef!.child("typingIndicator").queryOrderedByValue().queryEqual(toValue: true)

  private var newMessageRefHandle: FIRDatabaseHandle?
  private var updatedMessageRefHandle: FIRDatabaseHandle?

  private var messages: [JSQMessage] = []
  private var photoMessageMap = [String: JSQPhotoMediaItem]()

  private var localTyping = false
  var channel: Channel? {
    didSet {
      title = channel?.name
    }
  }

  var isTyping: Bool {
    get {
      return localTyping
    }
    set {
      localTyping = newValue
      userIsTypingRef.setValue(newValue)
    }
  }

  lazy var outgoingBubbleImageView: JSQMessagesBubbleImage = self.setupOutgoingBubble()
  lazy var incomingBubbleImageView: JSQMessagesBubbleImage = self.setupIncomingBubble()

  // MARK: View Lifecycle

  override func viewDidLoad() {
    super.viewDidLoad()
    self.senderId = FIRAuth.auth()?.currentUser?.uid
    observeMessages()

    // No avatars
    collectionView!.collectionViewLayout.incomingAvatarViewSize = CGSize.zero
    collectionView!.collectionViewLayout.outgoingAvatarViewSize = CGSize.zero
  }

  override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
    observeTyping()
  }

  deinit {
    if let refHandle = newMessageRefHandle {
      messageRef.removeObserver(withHandle: refHandle)
    }
    if let refHandle = updatedMessageRefHandle {
      messageRef.removeObserver(withHandle: refHandle)
    }
  }

  // MARK: Collection view data source (and related) methods

  override func collectionView(_ collectionView: JSQMessagesCollectionView!, messageDataForItemAt indexPath: IndexPath!) -> JSQMessageData! {
    return messages[indexPath.item]
  }

  override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return messages.count
  }

  override func collectionView(_ collectionView: JSQMessagesCollectionView!, messageBubbleImageDataForItemAt indexPath: IndexPath!) -> JSQMessageBubbleImageDataSource! {
    let message = messages[indexPath.item] // 1
    if message.senderId == senderId { // 2
      return outgoingBubbleImageView
    } else { // 3
      return incomingBubbleImageView
    }
  }

  override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let cell = super.collectionView(collectionView, cellForItemAt: indexPath) as! JSQMessagesCollectionViewCell

    let message = messages[indexPath.item]

    if message.senderId == senderId { // 1
      cell.textView?.textColor = UIColor.white // 2
    } else {
      cell.textView?.textColor = UIColor.black // 3
    }

    return cell
  }

  override func collectionView(_ collectionView: JSQMessagesCollectionView!, avatarImageDataForItemAt indexPath: IndexPath!) -> JSQMessageAvatarImageDataSource! {
    return nil
  }

  override func collectionView(_ collectionView: JSQMessagesCollectionView!, layout collectionViewLayout: JSQMessagesCollectionViewFlowLayout!, heightForMessageBubbleTopLabelAt indexPath: IndexPath!) -> CGFloat {
    return 15
  }

  override func collectionView(_ collectionView: JSQMessagesCollectionView?, attributedTextForMessageBubbleTopLabelAt indexPath: IndexPath!) -> NSAttributedString? {
    let message = messages[indexPath.item]
    switch message.senderId {
    case senderId:
      return nil
    default:
      guard let senderDisplayName = message.senderDisplayName else {
        assertionFailure()
        return nil
      }
      return NSAttributedString(string: senderDisplayName)
    }
  }

  // MARK: Firebase related methods

  private func observeMessages() {
    messageRef = channelRef!.child("messages")
    let messageQuery = messageRef.queryLimited(toLast:25)

    // We can use the observe method to listen for new
    // messages being written to the Firebase DB
    newMessageRefHandle = messageQuery.observe(.childAdded, with: { (snapshot) -> Void in
      let messageData = snapshot.value as! Dictionary<String, String>

      if let id = messageData["senderId"] as String!, let name = messageData["senderName"] as String!, let text = messageData["text"] as String!, text.characters.count > 0 {
        self.addMessage(withId: id, name: name, text: text)
        self.finishReceivingMessage()
      } else if let id = messageData["senderId"] as String!, let photoURL = messageData["photoURL"] as String! {
        if let mediaItem = JSQPhotoMediaItem(maskAsOutgoing: id == self.senderId) {
          self.addPhotoMessage(withId: id, key: snapshot.key, mediaItem: mediaItem)

          if photoURL.hasPrefix("gs://") {
            self.fetchImageDataAtURL(photoURL, forMediaItem: mediaItem, clearsPhotoMessageMapOnSuccessForKey: nil)
          }
        }
      } else {
        print("Error! Could not decode message data")
      }
    })

    // We can also use the observer method to listen for
    // changes to existing messages.
    // We use this to be notified when a photo has been stored
    // to the Firebase Storage, so we can update the message data
    updatedMessageRefHandle = messageRef.observe(.childChanged, with: { (snapshot) in
      let key = snapshot.key
      let messageData = snapshot.value as! Dictionary<String, String>

      if let photoURL = messageData["photoURL"] as String! {
        // The photo has been updated.
        if let mediaItem = self.photoMessageMap[key] {
          self.fetchImageDataAtURL(photoURL, forMediaItem: mediaItem, clearsPhotoMessageMapOnSuccessForKey: key)
        }
      }
    })
  }

  private func fetchImageDataAtURL(_ photoURL: String, forMediaItem mediaItem: JSQPhotoMediaItem, clearsPhotoMessageMapOnSuccessForKey key: String?) {
    let storageRef = FIRStorage.storage().reference(forURL: photoURL)
    storageRef.data(withMaxSize: INT64_MAX){ (data, error) in
      if let error = error {
        print("Error downloading image data: \(error)")
        return
      }

      storageRef.metadata(completion: { (metadata, metadataErr) in
        if let error = metadataErr {
          print("Error downloading metadata: \(error)")
          return
        }

        if (metadata?.contentType == "image/gif") {
          mediaItem.image = UIImage.gifWithData(data!)
        } else {
          mediaItem.image = UIImage.init(data: data!)
        }
        self.collectionView.reloadData()

        guard key != nil else {
          return
        }
        self.photoMessageMap.removeValue(forKey: key!)
      })
    }
  }

  private func observeTyping() {
    let typingIndicatorRef = channelRef!.child("typingIndicator")
    userIsTypingRef = typingIndicatorRef.child(senderId)
    userIsTypingRef.onDisconnectRemoveValue()
    usersTypingQuery = typingIndicatorRef.queryOrderedByValue().queryEqual(toValue: true)

    usersTypingQuery.observe(.value) { (data: FIRDataSnapshot) in

      // You're the only typing, don't show the indicator
      if data.childrenCount == 1 && self.isTyping {
        return
      }

      // Are there others typing?
      self.showTypingIndicator = data.childrenCount > 0
      self.scrollToBottom(animated: true)
    }
  }

  override func didPressSend(_ button: UIButton!, withMessageText text: String!, senderId: String!, senderDisplayName: String!, date: Date!) {
    // 1
    let itemRef = messageRef.childByAutoId()

    // 2
    let messageItem = [
      "senderId": senderId!,
      "senderName": senderDisplayName!,
      "text": text!,
    ]

    // 3
    itemRef.setValue(messageItem)

    // 4
    JSQSystemSoundPlayer.jsq_playMessageSentSound()

    // 5
    finishSendingMessage()
    isTyping = false
  }

  func sendPhotoMessage() -> String? {
    let itemRef = messageRef.childByAutoId()

    let messageItem = [
      "photoURL": imageURLNotSetKey,
      "senderId": senderId!,
      ]

    itemRef.setValue(messageItem)

    JSQSystemSoundPlayer.jsq_playMessageSentSound()

    finishSendingMessage()
    return itemRef.key
  }

  func setImageURL(_ url: String, forPhotoMessageWithKey key: String) {
    let itemRef = messageRef.child(key)
    itemRef.updateChildValues(["photoURL": url])
  }

  // MARK: UI and User Interaction

  private func setupOutgoingBubble() -> JSQMessagesBubbleImage {
    let bubbleImageFactory = JSQMessagesBubbleImageFactory()
    return bubbleImageFactory!.outgoingMessagesBubbleImage(with: UIColor.jsq_messageBubbleBlue())
  }

  private func setupIncomingBubble() -> JSQMessagesBubbleImage {
    let bubbleImageFactory = JSQMessagesBubbleImageFactory()
    return bubbleImageFactory!.incomingMessagesBubbleImage(with: UIColor.jsq_messageBubbleLightGray())
  }

  override func didPressAccessoryButton(_ sender: UIButton) {
    let picker = UIImagePickerController()
    picker.delegate = self
    if (UIImagePickerController.isSourceTypeAvailable(UIImagePickerControllerSourceType.camera)) {
      picker.sourceType = UIImagePickerControllerSourceType.camera
    } else {
      picker.sourceType = UIImagePickerControllerSourceType.photoLibrary
    }

    present(picker, animated: true, completion:nil)
  }

  private func addMessage(withId id: String, name: String, text: String) {
    if let message = JSQMessage(senderId: id, displayName: name, text: text) {
      messages.append(message)      
    }
  }

  private func addPhotoMessage(withId id: String, key: String, mediaItem: JSQPhotoMediaItem) {
    if let message = JSQMessage(senderId: id, displayName: "", media: mediaItem) {
      messages.append(message)

      if (mediaItem.image == nil) {
        photoMessageMap[key] = mediaItem
      }

      collectionView.reloadData()
    }
  }

  // MARK: UITextViewDelegate methods

  override func textViewDidChange(_ textView: UITextView) {
    super.textViewDidChange(textView)
    // If the text is not empty, the user is typing
    isTyping = textView.text != ""
  }

}

// MARK: Image Picker Delegate
extension ChatViewController: UIImagePickerControllerDelegate, UINavigationControllerDelegate {
  func imagePickerController(_ picker: UIImagePickerController,
                             didFinishPickingMediaWithInfo info: [String : Any]) {

    picker.dismiss(animated: true, completion:nil)

    // 1
    if let photoReferenceUrl = info[UIImagePickerControllerReferenceURL] as? URL {
      // Handle picking a Photo from the Photo Library
      // 2
      let assets = PHAsset.fetchAssets(withALAssetURLs: [photoReferenceUrl], options: nil)
      let asset = assets.firstObject

      // 3
      if let key = sendPhotoMessage() {
        // 4
        asset?.requestContentEditingInput(with: nil, completionHandler: { (contentEditingInput, info) in
          let imageFileURL = contentEditingInput?.fullSizeImageURL

          // 5
          let path = "\(FIRAuth.auth()?.currentUser?.uid)/\(Int(Date.timeIntervalSinceReferenceDate * 1000))/\(photoReferenceUrl.lastPathComponent)"

          // 6
          self.storageRef.child(path).putFile(imageFileURL!, metadata: nil) { (metadata, error) in
            if let error = error {
              print("Error uploading photo: \(error.localizedDescription)")
              return
            }
            // 7
            self.setImageURL(self.storageRef.child((metadata?.path)!).description, forPhotoMessageWithKey: key)
          }
        })
      }
    } else {
      // Handle picking a Photo from the Camera - TODO
    }
  }

  func imagePickerControllerDidCancel(_ picker: UIImagePickerController) {
    picker.dismiss(animated: true, completion:nil)
  }
}

Answer 1

问题在于您的代码的这一部分：

guard let senderDisplayName = message.senderDisplayName else {
    assertionFailure()
    return nil
}

assertionFailure()必须链接到另一个运行assert(false)的函数或一些等效的函数。 assert(_)用于验证特定参数或比较是否返回true，如果不是，则会使应用程序崩溃。如果它是生产版本（如App Store上的版本），应用程序不会崩溃，因为断言用于调试目的。

基本上，必须使用guard语句来验证message.senderDisplayName是否对某些值（不是nil）不可用。如果message.senderDisplayName为nil，那么运行守卫下面的代码是没有意义的，应该运行后卫的内容。 assertionFailure()会在测试期间崩溃应用程序，在生产过程中它将被忽略。如果忽略它，将返回该函数的nil，并且它将继续运行，因为没有任何反应。