swift - 在 Collection View 中随机上传帖子 - Swift 和 Firebase

Question

我一直在重构我的代码，但现在我在帖子上遇到了问题。

每当我将新帖子添加到 Collection View 时，它都会无序地添加到随机单元格中，而不是添加到第一篇帖子中。

我知道原因是 fetchuser 函数，并且从我被告知的异步加载情况来看，但不知道该怎么做才能纠正这个问题。

有人可以帮我弄清楚该怎么做才能将我的帖子添加到第一个单元格中吗？

 @objc func observePostsAdoption() {
    let postsRef = Database.database().reference().child("posts")
    postsRef.queryOrdered(byChild: "postType").queryEqual(toValue: "adopt").observe(.value) { (snapshot) in
        var tempPost = [Posts]()
        for child in snapshot.children {
            if let childSnapshot = child as? DataSnapshot {
                let dict = childSnapshot.value as? [String: Any]
                let newAdoptiondPost = Posts.transformPost(dict: dict!)
                //This will look up all users at once
                self.fetchUser(userid: newAdoptiondPost.userid!, completed: {
                 tempPost.insert(newAdoptiondPost, at: 0)
                    DispatchQueue.main.async {
                        self.postsadoption = tempPost
                        self.adoptionCollectionView.reloadData()
                        self.refresherAdoption.endRefreshing()
                    }
            })
            }

        }
    }
}

func fetchUser(userid: String, completed:  @escaping ()-> Void ) {

    Database.database().reference().child("users").child(userid).observeSingleEvent(of: .value) { (snapshot) in
        if let dict = snapshot.value as? [String: Any] {
            let user = UserProfile.transformUser(dict: dict)
            self.users.insert(user, at: 0)
            completed()
        }
    }

}

这是我的帖子结构

class Posts {

//UserView
var uid: String?
var author: UserProfile?
var timestamp: Date?
var userid: String?

func getDateFormattedString() -> String {
    let formatter = DateFormatter()
    formatter.dateFormat = "MMM d, HH:mm"
    return formatter.string(from: self.timestamp!)
}

//Image
var photoUrl: URL?

//PostInformation View
var city: String?
var municipality: String?
var name: String?
var breed : String?
var phone : String?
var address : String?
var petType: String?
var genderType: String?
var comments: String?

}

扩展帖子{

static func transformPost(dict: [String: Any]) -> Posts {

    let post = Posts()

    //Post Picture
    let photoUrl = dict["photoUrl"] as? String
    post.photoUrl = URL(string: photoUrl!)

    //INFO POSTS
    post.userid = dict["userid"] as? String
    post.city = dict["city"] as? String
    post.municipality = dict["municipality"] as? String
    post.name = dict["name"] as? String
    post.breed = dict["breed"] as? String
    post.phone = dict["phone"] as? String
    post.address = dict["address"] as? String
    post.comments = dict["comments"] as? String
    post.petType = dict["petType"] as? String
    post.genderType = dict["gender"] as? String
    let timestamp = dict["timestamp"] as? Double
    post.timestamp = Date(timeIntervalSince1970: timestamp!/1000)

    return post

}

}

Answer 1

如果您已经有按帖子类型排序的帖子，您可以根据时间戳进行排序。例如

@objc func observePostsAdoption() {
        let postsRef = Database.database().reference().child("posts")
        postsRef.queryOrdered(byChild: "postType").queryEqual(toValue: "adopt").observe(.value) { (snapshot) in
            var tempPost = [Posts]()
            for child in snapshot.children {
                if let childSnapshot = child as? DataSnapshot {
                    let dict = childSnapshot.value as? [String: Any]
                    let newAdoptiondPost = Posts.transformPost(dict: dict!)
                    //This will look up all users at once
                    self.fetchUser(userid: newAdoptiondPost.userid!, completed: {
                        tempPost.insert(newAdoptiondPost, at: 0)
                        DispatchQueue.main.async {
                            self.postsadoption = tempPost
                            self.postsadoption.sort { (p1, p2) -> Bool in
                                return p1.timeStamp?.compare(p2.timeStamp!) == .orderdDescending
                            }
                            self.adoptionCollectionView.reloadData()
                            self.refresherAdoption.endRefreshing()
                        }
                    })
                }

            }
        }
    }

这样，帖子采用数组将根据您拥有的时间戳进行排序。