[CIS-1087] Fix data races in message list's message count (#1347)

GetStream · Aug 10, 2021 · e657a92 · e657a92
1 parent 08b7477
commit e657a92
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Showing 4 changed files with 37 additions and 8 deletions.
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -5,6 +5,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ### 🔄 Changed
 
+- Fixed race condition on `ChatMessageListVC` and `ChatThreadVC` that caused `UITableView` crashes [#1347](https://github.com/GetStream/stream-chat-swift/pull/1347)
 - Added `GalleryAttachmentViewInjector.galleryViewAspectRatio` to control the aspect ratio of a gallery inside a message cell [#1300](https://github.com/GetStream/stream-chat-swift/pull/1300)
 
 # [4.0.0-beta.9](https://github.com/GetStream/stream-chat-swift/releases/tag/4.0.0-beta.9)

diff --git a/Sources/StreamChatUI/ChatMessageList/ChatMessageListVC.swift b/Sources/StreamChatUI/ChatMessageList/ChatMessageListVC.swift
@@ -24,6 +24,9 @@ open class ChatMessageListVC:
     ChatMessageListScrollOverlayDataSource {
     /// Controller for observing data changes within the channel
     open var channelController: ChatChannelController!
+
+    /// We use private property for channels count so we can update it inside `performBatchUpdates` as [documented](https://developer.apple.com/documentation/uikit/uicollectionview/1618045-performbatchupdates#discussion)
+    private var numberOfMessages = 0
 
     public var client: ChatClient {
         channelController.client
@@ -106,6 +109,7 @@ open class ChatMessageListVC:
 
     override open func setUp() {
         super.setUp()
+        updateNumberOfMessages()
 
         let longPress = UILongPressGestureRecognizer(target: self, action: #selector(handleLongPress))
         longPress.minimumPressDuration = 0.33
@@ -317,7 +321,11 @@ open class ChatMessageListVC:
 
     /// Updates the collection view data with given `changes`.
     open func updateMessages(with changes: [ListChange<ChatMessage>], completion: (() -> Void)? = nil) {
-        listView.updateMessages(with: changes, completion: completion)
+        listView.updateMessages(
+            with: changes,
+            onMessagesCountUpdate: updateNumberOfMessages,
+            completion: completion
+        )
     }
 
     open func messageForIndexPath(_ indexPath: IndexPath) -> ChatMessage {
@@ -563,7 +571,7 @@ open class ChatMessageListVC:
     }
 
     open func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
-        channelController.messages.count
+        numberOfMessages
     }
 
     open func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
@@ -588,6 +596,10 @@ open class ChatMessageListVC:
         return !listView.isLastCellFullyVisible && isMoreContentThanOnePage
     }
 
+    private func updateNumberOfMessages() {
+        numberOfMessages = channelController.messages.count
+    }
+
     // MARK: - UIGestureRecognizerDelegate
 
     open func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldReceive touch: UITouch) -> Bool {

diff --git a/Sources/StreamChatUI/ChatMessageList/ChatMessageListView.swift b/Sources/StreamChatUI/ChatMessageList/ChatMessageListView.swift
@@ -171,13 +171,15 @@ open class ChatMessageListView: UITableView, Customizable, ComponentsProvider {
     /// Updates the table view data with given `changes`.
     open func updateMessages(
         with changes: [ListChange<ChatMessage>],
+        onMessagesCountUpdate: () -> Void = {},
         completion: (() -> Void)? = nil
     ) {
         var shouldScrollToBottom = false
 
         guard let _ = collectionUpdatesMapper.mapToSetsOfIndexPaths(
             changes: changes,
             onConflict: {
+                onMessagesCountUpdate()
                 reloadData()
             }
         ) else { return }
@@ -210,6 +212,7 @@ open class ChatMessageListView: UITableView, Customizable, ComponentsProvider {
                     self.deleteRows(at: [index], with: .fade)
                 }
             }
+            onMessagesCountUpdate()
         }, completion: { _ in
             if shouldScrollToBottom {
                 self.scrollToBottomAction = .init { [weak self] in

diff --git a/Sources/StreamChatUI/ChatMessageList/ChatThreadVC.swift b/Sources/StreamChatUI/ChatMessageList/ChatThreadVC.swift
@@ -28,6 +28,9 @@ open class ChatThreadVC:
 
     /// Controller for observing data changes within the parent thread message.
     open var messageController: ChatMessageController!
+
+    /// We use private property for channels count so we can update it inside `performBatchUpdates` as [documented](https://developer.apple.com/documentation/uikit/uicollectionview/1618045-performbatchupdates#discussion)
+    private var numberOfMessages = 0
 
     /// Observer responsible for setting the correct offset when keyboard frame is changed
     open lazy var keyboardObserver = ChatMessageListKeyboardObserver(
@@ -79,6 +82,7 @@ open class ChatThreadVC:
 
     override open func setUp() {
         super.setUp()
+        updateNumberOfMessages()
 
         let longPress = UILongPressGestureRecognizer(target: self, action: #selector(handleLongPress))
         longPress.minimumPressDuration = 0.33
@@ -92,6 +96,11 @@ open class ChatThreadVC:
         messageComposerVC.setDelegate(self)
         messageComposerVC.channelController = channelController
         messageComposerVC.userSearchController = userSuggestionSearchController
+
+        messageController.delegate = self
+        messageController.synchronize()
+        messageController.loadPreviousReplies()
+
         if let message = messageController.message {
             messageComposerVC.content.threadMessage = message
         }
@@ -101,10 +110,6 @@ open class ChatThreadVC:
         channelController.setDelegate(self)
         channelController.synchronize()
 
-        messageController.delegate = self
-        messageController.synchronize()
-        messageController.loadPreviousReplies()
-
         if let cid = channelController.cid {
             headerView.channelController = channelController.client.channelController(for: cid)
         }
@@ -235,7 +240,7 @@ open class ChatThreadVC:
     }
 
     open func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
-        messages.count
+        numberOfMessages
     }
 
     open func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
@@ -290,7 +295,11 @@ open class ChatThreadVC:
 
     /// Updates the collection view data with given `changes`.
     open func updateMessages(with changes: [ListChange<ChatMessage>], completion: (() -> Void)? = nil) {
-        listView.updateMessages(with: changes, completion: completion)
+        listView.updateMessages(
+            with: changes,
+            onMessagesCountUpdate: updateNumberOfMessages,
+            completion: completion
+        )
     }
 
     /// Presents custom actions controller with all possible actions with the selected message.
@@ -498,6 +507,10 @@ open class ChatThreadVC:
             .string(from: messageForIndexPath(indexPath).createdAt)
     }
 
+    private func updateNumberOfMessages() {
+        numberOfMessages = messages.count
+    }
+
     // MARK: - UIGestureRecognizerDelegate
 
     open func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldReceive touch: UITouch) -> Bool {