swift - 使用swift在firebase中获取嵌套数据

Question

我正在尝试在我的应用程序上实现对帖子的评论，但在获取帖子中称为“评论”的嵌套数据时遇到问题。如果我的 firebase 数据库结构类似于图片，我该如何正确地将评论下载为 messageComments 数组？

func getFeedMessages(handler: @escaping (_ feedMessages:[FeedMessages]) -> ()){
        var feedMessagesArray = [FeedMessages]()
        var commentArray = [messageComments]()


        REF_FEEDMESSAGES.observeSingleEvent(of: .value) { (feedMessagesSnapshot) in

            guard let feedMessagesSnapshot = feedMessagesSnapshot.children.allObjects as? [DataSnapshot] else {return}
            for messages in feedMessagesSnapshot {

                let content = messages.childSnapshot(forPath: "content").value as? String ?? "Joe Flacco is an elite QB"
                let icon = messages.childSnapshot(forPath: "icon").value as? String ?? "none"
                let color = messages.childSnapshot(forPath: "color").value as? String ?? "bop"
                let date = messages.childSnapshot(forPath: "date").value as? String ?? "0"
                let comments = messages.childSnapshot(forPath: "comments").value as? [messageComments] ?? []
                let userName = messages.childSnapshot(forPath: "userName").value as? String ?? "Anonymous"

                let messages = FeedMessages(content: content, color: color, icon: icon, date: date, comments: comments, userName: userName)
                feedMessagesArray.append(messages)
            }

            handler(feedMessagesArray)
        }
    }

Answer 1

您不能访问这样的评论。您需要使用 encodable 来执行此操作，或者由于您手动访问每个快照中的值，您可以像这样访问它:

let comments = messages.childSnapshot(forPath: "comments").value as? [String: Any]
let comment1 = comments?["comment1"] as? String ?? "comment1"
let comment2 = comments?["comment2"] as? String ?? "comment2"

然后您需要通过调用您的messageComments 初始化程序来正常初始化您的对象messageComments。另外，我建议您的类(class)名称以大写字母开头。

编辑:对于手动加载评论，我建议这样做:

if let comments = comments { 
    for comment in comments.values {
       // here your access your comment as you want, you need to cast as string
    }
}