我有一个 Firebase 快照侦听器，它检查新文档，将它们添加到数组（collectionView 数据源），然后重新加载 collectionView。但是，我在 collectionView 中得到了重复的单元格。我的 Firestore 集合中目前有 3 个对象，但它们总共被复制了 9 个单元格。
我什至添加了对索引的检查，因此 reloadData 仅在到达数组末尾后发生。以下是相关代码：
messageListener = query.addSnapshotListener { querySnapshot, error in
guard let snapshot = querySnapshot else {
print("Error listening for channel updates: \(error?.localizedDescription ?? "No error")")
return
}
snapshot.documentChanges.forEach { change in
if change.type == .added {
for document in snapshot.documents{
....
let newMessage = Message(sender: newSender, messageId: document.documentID, sentDate: date, text: text)
self.messages.append(newMessage)
guard let index = snapshot.documents.index(of: document) else {return}
if index == (snapshot.documents.count - 1) {
self.messagesCollectionView.reloadData()
}
}
}
}
}
它正确地对索引进行倒计时，因此最终达到 2 == 2 以重新加载数据。但是，它会再次启动该过程另外两次，总共 3 次（3 个对象加载了 3 次，总共 9 个单元格）。知道如何改进此逻辑流程以停止重复吗？
谢谢！！
编辑 1
extension ChatViewController: MessagesDataSource {
func currentSender() -> Sender {
//guard let currentUserID = User.current?.key else {return nil}
let newSender = Sender(id: (User.current?.key)!, displayName: (User.current?.username)!)
return newSender
}
func numberOfSections(in messagesCollectionView: MessagesCollectionView) -> Int {
return 1
}
func numberOfItems(inSection section: Int, in messagesCollectionView: MessagesCollectionView) -> Int {
return messages.count
}
func messageForItem(at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> MessageType {
return messages[indexPath.section]
func cellTopLabelAttributedText(for message: MessageType, at indexPath: IndexPath) -> NSAttributedString? {
return NSAttributedString(string: MessageKitDateFormatter.shared.string(from: message.sentDate), attributes: [NSAttributedString.Key.font: UIFont.boldSystemFont(ofSize: 10), NSAttributedString.Key.foregroundColor: UIColor.darkGray])
}
func messageTopLabelAttributedText(for message: MessageType, at indexPath: IndexPath) -> NSAttributedString? {
let name = message.sender.displayName
return NSAttributedString(string: name, attributes: [NSAttributedString.Key.font: UIFont.preferredFont(forTextStyle: .caption1)])
}
func messageBottomLabelAttributedText(for message: MessageType, at indexPath: IndexPath) -> NSAttributedString? {
let dateString = formatter.string(from: message.sentDate)
return NSAttributedString(string: dateString, attributes: [NSAttributedString.Key.font: UIFont.preferredFont(forTextStyle: .caption2)])
}
}
}