swift 从 firebase 检索快照节点的最佳方法是什么

Question

如何从此快照中检索 senderId。 ChildAdded 必须使用并且下面的 FirRef 必须保持不变。

这是我当前从 firebase 检索数据的函数

 func retrieveInfo(completion: (result: String)->()) {
       fireBaseAPI().childRef("version_one/frontEnd/post/\(self.previousViewMessageId)").observeEventType(.ChildAdded, withBlock: {snapshot in



     })

这是正在打印的快照

Snap (postDescription) Description here
Snap (postTitle) What do you need done
Snap (receiverId) RYclS9Qy4vRr6gp8JbfoztSYQnL2
Snap (senderId) niZKOcnoh0cdFpF2K26bxugw1hz1
Snap (status) 0
Snap (messages) {
    "-KRqOqd2POJYpCNSSumG" =     {
        mediaType = TEXT;
        senderDisplayName = "";
        senderId = niZKOcnoh0cdFpF2K26bxugw1hz1;
        text = iPhone;
    };
}

检索任何显示 Snap 的节点的最佳方法是什么

这是 Firebase Json

 {
  "version_one" : {
    "frontEnd" : {
      "post" : {
        "-KRoucvwAs1jBaoNahDP" : {
          "messages" : {
            "-KRqOqd2POJYpCNSSumG" : {
              "mediaType" : "TEXT",
              "senderDisplayName" : "",
              "senderId" : "niZKOcnoh0cdFpF2K26bxugw1hz1",
              "text" : "iPhone"
            }
          },
          "postDescription" : "Description here",
          "postTitle" : "What do you need done",
          "receiverId" : "RYclS9Qy4vRr6gp8JbfoztSYQnL2",
          "senderId" : "niZKOcnoh0cdFpF2K26bxugw1hz1",
          "status" : 0
        }
      },

Answer 1

func retrieveInfo(completion: (result: String)->()) {
   fireBaseAPI().childRef("version_one/frontEnd/post/\(self.previousViewMessageId)").observeEventType(.ChildAdded, withBlock: {snapshot in
    if let messageDict = snapshot.value in [String:AnyObject]{

                  let senderId = messageDict["senderId"] as! String
              .....


      }

 })