swift什么是从firebase检索snap节点的最佳方式

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。

这是我目前的FUNC从火力

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



    }) 

检索数据这是正在打印

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; 
    }; 
} 

什么是检索任何说快

节点的最佳途径快照

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 
       ..... 


     } 

})