swift - 如何从 Firebase 一次检索整个对象？

Question

我刚刚开始使用 Firebase 进行 Swift 编程。我设法使用以下方法从 Json 中获取了一些数据:

   let ref = FIRDatabase.database().reference()
        ref.child("Posts").child("1").child("Post").child("Like").observeSingleEvent(of: .value, with: { (Snapshot) in
            let Value = Snapshot.value as? Int
            print(Value!)
        })

但是，我试图先获取整个对象，然后再获取每个元素的值。所以这是我的尝试，但我的应用程序不断终止:

let ref = FIRDatabase.database().reference()
        ref.child("Posts").child("1").child("Post").observeSingleEvent(of: FIRDataEventType.childAdded, with: { (snapshot) in
                print(snapshot.children.value(forKey: "Like") as? Int)
                print(snapshot.children.value(forKey: "Image") as? String)
        })

知道我在哪里犯了错误吗？ 这是我的 Json:

{
    "Posts": {
        "1": {
            "Post": {
                "Poster_ID": "ID",
                "Post_Time_stamp": "12:12:12AM",
                "Image": "img.png",
                "Video": "video.mov",
                "Like": "3",
                "Dislike": "0",
                "Massage": {
                    "Massage_ID": "MSG_ID",
                    "Massager": "id",
                    "Massage_Time_stamp": "12:12:12PM",
                    "Massage_content": "comment"
                }


            }
        },
        "2": {
            "Post": {
                "Poster_ID": "ID",
                "Post_Time_stamp": "12:12:12AM",
                "Image": "img.png",
                "Video": "video.mov",
                "Like": "3",
                "Dislike": "0",
                "Massage": {
                    "Massage_ID": "MSG_ID",
                    "Massager": "id",
                    "Massage_Time_stamp": "12:12:12PM",
                    "Massage_content": "comment"
                }


            }
        }
    },
    "User": {
        "1": {
            "User_name": "name",
            "User_pass": "pass",
            "User_avatar": "img.png"
        },
        "2": {
            "User_name": "name",
            "User_pass": "pass",
            "User_avatar": "img.png"
        }
    }
}

Answer 1

先尝试打印快照，看看是否能检索到任何内容，如果不能，试试这个

使用 FIRDataEventType 作为 .value 而不是 .childAdded。由于 .childAdded 仅在将子节点添加到该引用节点时触发，因此 .value 检索当前值作为该引用点..

let ref = FIRDatabase.database().reference()
    ref.child("Posts").child("1").child("Post").observeSingleEvent(of: .value, with: { (snapshot) in
            print(snapshot)
            print(snapshot.children.value(forKey: "Like") as? Int)
            print(snapshot.children.value(forKey: "Image") as? String)
    })