swift 3 : How to retry Firebase upload on failure

Question

我正在 Firebase 中初始化一些数据，我将用它们来跟踪用户的事件。我需要确保这些数据写入 Firebase，所以我想知道确保关键上传成功的最佳实践是什么？

static func createUserActivityCounts(uid: String) {
        DispatchQueue.global(qos: .background).asyncAfter(deadline: .now() + .seconds(5)) {
            let databaseReference = Database.database().reference()
            let userCounts: [String: Any] = ["posts": 0,
                                             "comments": 0,
                                             "likes": 0]
            databaseReference.child("userActivity").child(uid).child("counts").setValue(userCounts) { (error, ref) -> Void in
                if error != nil {
                    print(error!.localizedDescription)
                }
            }
        }
    }

Answer 1

我认为解决此问题的最佳方法是在尝试查询关键上传时检查该值是否存在。如果该值不存在，则对其进行初始化。这是我为处理此问题而编写的函数。

private func getUserActivityCounts() {
    if let uid = Auth.auth().currentUser?.uid {
    userRef.child("userActivity").child(uid).child("counts").observeSingleEvent(of: .value, with: { snap in
            if !snap.exists() {
                // create user counts
                if let uid = Auth.auth().currentUser?.uid {
                    DatabaseFunctions.createUserActivityCounts(uid: uid)
                }
            }
            if let counts = snap.value as? [String: Any] {
                if let numberOfLikes = counts["likes"] as? Int, let commentCount = counts["comments"] as? Int, let postCount = counts["posts"] as? Int {
                    DispatchQueue.main.async {
                        self.headerRef.postCount.text = String(postCount)
                        self.headerRef.commentCount.text = String(commentCount)
                        self.headerRef.likeCount.text = String(numberOfLikes)
                        self.collectionView.reloadData()
                    }
                    self.numberOfUserPosts = postCount
                    self.commentCount = commentCount
                    self.likeCount = numberOfLikes
                }
            }
        })
    }
}