使用 Firestore 差异的正确方法

Question

我正在调用此函数以从 Firestore 中检索用户： 每次修改用户时，我都想更新用户数组。

func fetchUsers( complete: @escaping ( _ success: Bool, _ users: [User], _ error: Error? )->()) {
    //self.users = []
    let circleId  = UserDefaults.standard.string(forKey: "circleId") ?? ""
    DataService.call.REF_CIRCLES.document(circleId).collection("insiders").order(by: "position", descending: false).addSnapshotListener { querySnapshot, error in
        guard let snapshot = querySnapshot else {
            print("Error fetching snapshots: \(error!)")
            return
        }


        snapshot.documentChanges.forEach { diff in

            if (diff.type == .added) {
                let data = diff.document.data()
                let id = diff.document.documentID
                let user = User(key: id, data: data)
                self.users.append(user)
                complete(true, self.users, nil)
            }

            if (diff.type == .modified) {
                // Update users array if user data is modified
                if !self.users.isEmpty {
                    self.users = []
                let data = diff.document.data()
                let id = diff.document.documentID
                let user = User(key: id, data: data)
                self.users.append(user)
                complete(true, self.users, nil)
                }
            }

            if (diff.type == .removed) {
                print("Removed user: \(diff.document.data())")
            }
        }
    }
}

但是，如果只修改了一个用户并且我的 collectionview 重新加载然后只显示一个用户，我的数组总是返回 1！我如何 即使只修改了一个用户，也返回所有用户？ 谢谢

新功能：

func fetchUsers( complete: @escaping ( _ success: Bool, _ users: [User], _ error: Error? )->()) {
    self.users = []
    let circleId  = UserDefaults.standard.string(forKey: "circleId") ?? ""
    DataService.call.REF_CIRCLES.document(circleId).collection("insiders").order(by: "position", descending: false).addSnapshotListener { querySnapshot, error in
        guard let snapshot = querySnapshot else {
            print("Error fetching snapshots: \(error!)")
            return
        }

             snapshot.documents.forEach { diff in
                let data = diff.data()
                let id = diff.documentID
                let user = User(key: id, data: data)
                self.users.append(user)
                complete(true, self.users, nil)
         }
    }
}

现在我在我的收藏视图中看到很多重复的用户

Answer 1

您正在循环访问 QuerySnapshot.documentChanges，其中仅包含自上次快照以来发生更改的文档。

要获取查询中的所有文档（而不仅仅是修改过的文档），请循环遍历 QuerySnapshot.documents：

DataService.call.REF_CIRCLES.document(circleId).collection("insiders").order(by: "position", descending: false).addSnapshotListener { querySnapshot, error in
    guard let snapshot = querySnapshot else {
        print("Error fetching snapshots: \(error!)")
        return
    }

    snapshot.documents.forEach { diff in
      ...