Question

我刚开始使用Firebase进行Swift编程。我设法使用以下内容从Json获取一些数据：

   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，但我的应用程序一直被终止：

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)
        })

知道我哪里弄错了吗？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

首先尝试打印snapshot，看看是否可以检索任何内容，请尝试此操作

将FIRDataEventType用作.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将当前值检索为该参考点。

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)
    })

Answer 2

如果您想要获取帖子对象，则需要访问value，同时注意childAdded事件，而不是let ref = FIRDatabase.database().reference() ref.child("Posts").child("1").child("Post") .observeSingleEvent(of: .value, with: { (snapshot) in if let dict = snapshot.value as? [String:Any] { print(dict["Like"] as? Int ?? 0) } })。

$(".framed-content").mCustomScrollbar({
    theme: "dark-2",
    scrollButtons:{ enable: true },
});

如何从Firebase立即检索整个对象？

2 个答案: