Swift CollectionView.reload 数据在 Firebase 中发生变化时不起作用？

Question

我目前有这个工作代码，它从 Firebase 中的 users 位置读取，其中包含每个用户的所有用户个人资料信息。我正在使用从 Firebase 返回的快照(数据)来构建我的数组并在 CollectionView 中显示用户。

我预期的行为(没有发生)是当 user 属性的值在 Firebase 中更改时(例如；online 状态更改为“离线” ) 这应该被推送到我的应用程序，以便 CollectionView 更新，因此不会显示刚刚“离线”的用户。

我在下面使用的 Firebase 查询是否正确？

self.REF_USERS.observeSingleEvent(of: .value , with: { (snapshot) in

                    guard let usersSnapshot = snapshot.children.allObjects as? [DataSnapshot] else { return }

                    for user in usersSnapshot{

                        let discoverable = user.childSnapshot(forPath: "discoverable").value as! Bool

                        if user.key == key && discoverable == true {

                            let uid = user.key
                            let name = user.childSnapshot(forPath: "name").value as! String
                            let email = user.childSnapshot(forPath: "email").value as! String
                            let profilePictureURL = user.childSnapshot(forPath: "profilePictureURL").value as! String

                            let birthday = user.childSnapshot(forPath: "birthday").value as! String
                            let firstName = user.childSnapshot(forPath: "firstName").value as! String
                            let lastName = user.childSnapshot(forPath: "lastName").value as! String
                            let gender = user.childSnapshot(forPath: "gender").value as! String
                            let discoverable = user.childSnapshot(forPath: "discoverable").value as! Bool
                            let online = user.childSnapshot(forPath: "online").value as! Bool

                            let discoveryPrefs = user.childSnapshot(forPath: "discoveryPrefs").value as! [String : Any]

                            let dictionary: [String : Any] = ["uid": uid, "name": name, "email": email, "profilePictureURL": profilePictureURL, "birthday": birthday, "firstName": firstName, "lastName": lastName, "gender": gender, "discoverable": discoverable, "online": online, "discoveryPrefs": discoveryPrefs]

                            let user = User(uid: uid, dictionary: dictionary)

                            users.append(user)

                        }//end if

                    }//end for

                    //filter out "remove" current user from array
                    let filteredUsers = users.filter({ (user: User) -> Bool in return !user.uid.contains(uid) })

                    handler(filteredUsers.shuffled(), true)//return a shuffled version of the array via handler

                })//end FIR snapshot call

这就是我使用上面的代码加载/重新加载数据的方式:

DataService.run.getUsersAtVenue(forVenueLocation: location, forUid: userId) { (users, successBool) in

            if successBool {
                self.users = users
                self.collectionView.reloadData()
                Utilities.run.dismissSVHUD(delay: 0.5)

            }
        }

Answer 1

您是否在主线程中，并且 users 发生了变化？尝试将其放入:

         DispatchQueue.main.async {
                if users.count > 0 {
                      self.users = users
                      self.collectionView.reloadData()
                      Utilities.run.dismissSVHUD(delay: 0.5)
                }  
        }