Firebase chat app crashes when clicking on table cell - ios

Question

I downloaded a demo chat application that runs perfectly but when I implement it into my own app it crashes and the code is exactly the same. The app gives you the ability to create a chat room and my app works up to this point but when you click on the chat room name that now appears on the table I get the following error:
Assertion failure in -[Irish_League_Grounds.ChatViewController viewWillAppear:], /Users/ryanball/Desktop/Irish League
Grounds/Pods/JSQMessagesViewController/JSQMessagesViewController/Controllers/JSQMessagesViewController.m:277
2017-05-17 17:32:55.815 Irish League Grounds[20456:681491]
Terminating app due to uncaught exception
'NSInternalInconsistencyException', reason: 'Invalid parameter not
satisfying: self.senderDisplayName != nil'
Here is my code for the two view controllers I'm segueing between:
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)
}
}
}
Here is the second view controller:
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

The problem lies with this section of your code:
guard let senderDisplayName = message.senderDisplayName else {
assertionFailure()
return nil
}
assertionFailure() must link to another function that runs assert(false) or some equivalent to that. assert(_) is meant to verify that a particular parameter or comparison returns true, or if it does not, it will crash the app. The app will not crash if it is a production build (like those on the App Store) because asserts are meant for debugging purposes.
Basically, the guard statement is necessary to verify that message.senderDisplayName is unwrappable to some value (not nil). If message.senderDisplayName is nil, then there is no point in running the code below the guard and the contents of the guard should be run instead. assertionFailure() will crash the app during testing and during production it will be ignored. When it is ignored, nil will be returned for the function and it will continue on as nothing happened.