How Parsing Firebase Fdatasnapshot JSON Data in Swift

how parsing Firebase FDatasnapshot json data in swift

Firebase is a NoSQL JSON database and has no schema and no tables. Data is stored with a 'tree' structure with nodes; parents and children.

You don't need to parse Firebase JSON data to access it, you can access it directly.

FDataSnapshots contain a .key, which is it's parent key in Firebase and .value. .Value may contain one node, or multiple nodes. The Value will have key:value pairs representing the data within the snapshot

So for your example you will have a Firebase structure like this

dogs
  dog_id_0
    title: "dog"
    type: "Alaskan Malamute"
    images:
        main: "dog.png"
        others:
            0: "1.png"
            1: "2.png"
  dog_id_1
    title: "another dog"
    type: "Boxer"
    images:
        main: "another_dog.png"
        others:
            0: "3.png"
            1: "4.png"

So, say you want to read in each dog_id_x node one at a time and print some values.

var ref = Firebase(url:"https://your-app.firebaseio.com/dogs")

ref.observeEventType(.ChildAdded, withBlock: { snapshot in
    println(snapshot.value.objectForKey("title"))
    println(snapshot.value.objectForKey("type"))
})

This will output

dog
Alaskan Malamute
another dog
Boxer

The dog_id_0 and dog_id_1 are node names created with the Firebase childByAutoId.

You could just as easily create a Dog class, and pass it the FDataSnapshot which will populate the class from the data within the snapshot.

firebase json deserialization swift

Instead of trying to fix all of that code, here's a clean, simple way to populate an array of rooms, where each room has an array of users.

Given a Firebase Structure similar to yours

  "rooms"
    "room_0"
      "groupChatName" : "Test123",
      "members"
        "user_0"
          "name" : "Barry"
        "user_1"
          "name" : "Maurice"
        "user_2"
          "name" : "Robin"

We start off with the RoomClass and UserClass. Note that I make those classes do the heavy lifting - they tear down the snapshot and store it's values.

Note that I treat the members child node as a snapshot so I can iterate over it while maintaining it's key: value pairs.

class RoomClass {
    var key = ""
    var groupChatName = ""
    var membersArray = [UserClass]()

    init(snapshot: DataSnapshot) {
        let dict = snapshot.value as! [String: Any]
        let membersSnap = snapshot.childSnapshot(forPath: "members")
        let snapKey = snapshot.key
        let groupName = dict["groupChatName"] as! String

        self.key = snapKey
        self.groupChatName = groupName

        for member in membersSnap.children {
            let memberSnap = member as! DataSnapshot
            let user = UserClass(snapshot: memberSnap)
            self.membersArray.append(user)
        }
    }
}

class UserClass {
    var key = ""
    var name = ""

    init(snapshot: DataSnapshot) {
        let dict = snapshot.value as! [String: Any]
        let snapKey = snapshot.key
        let userName = dict["name"] as! String
        self.key = snapKey
        self.name = userName
    }
}

We then define the array to store the rooms and the code to populate it

var roomsArray = [RoomClass]()

func doButton0Action() {
    let roomsRef = self.ref.child("rooms")
    roomsRef.observeSingleEvent(of: .value, with: { snapshot in

        for child in snapshot.children {
            let snap = child as! DataSnapshot
            let room = RoomClass(snapshot: snap)
            self.roomsArray.append(room)
        }

        //this just demonstrates the rooms and members are loaded
        for room in self.roomsArray {
            let groupChatName = room.groupChatName

            print(groupChatName)

            for user in room.membersArray {
                let userName = user.name
                print("  \(userName)")
            }
        }
    })
}

and the output

Test123
  Barry
  Maurice
  Robin

Trying to get data from firebase Swift

You are trying to return value out of completion handler.

Your function should be like:

private func findAverage(byUid uid: String, completion: @escaping (_ average: Int) -> Void) {
    // ...
    dbRef.observeSingleEvent(of: .value, with: { snapshot in
        guard let dict = snapshot.value as? [String: Any] else {
            return
        }
        totalRatings = dict["totalRatings"] as? Int ?? 0
        amountOfRatings = dict["amountOfRatings"] as? Int ?? 1

        completion((Int)(totalRatings / amountOfRatings))
    })
}

Something like this, check Swift docs (about completion handlers etc.).

Can I manipulate FDatasnapshot once I have queried for it?

Firebase accepts all the data in JSON format only. When you get a Datasnapshot of any perticular node of Firebase, you get the complete data below that node, which is in all a JSON only.

Once you get the Datasnapshot JSON you can parse it using any JSON library, depending on the platform you use.

You can refer here Datasnapshot Methods for more info.

What kind of object is the following output?

It's an FDataSnapshot. Since Firebase is a NoSQL/JSON data store, it serializes these snapshots to a pseudo-JSON structure when you print them. But when you need to get primitive values out of a snapshot, use the methods of FDataSnapshot like childSnapshotForPath: until you reach a simple property (FirstName and LastName in your sample) and then value to get the primitive value.

retrieving firebase data for iOS app using swift

Try this code

let jsonLocations = snapshot.valueInExportFormat() as! NSDictionary
let keys = jsonLocations.allKeys

for key in keys {
    let json = jsonLocations[key] as! [String: AnyObject]
    self.sections.append(Location(JSONObject: json))
}

Get data out of array of Firebase snapshots

I am not sure if the question can be answered without knowing how the array is built. One gotcha is the For-in loops variable is a NSFastEnumerationIterator so it needs to be downcast to what kind of 'thing' you want it to be. You may have done that so this is just for future reference.

That being said, I crafted up some code and broke it down a bit - maybe it will point you in the right direction.

The code below reads in all nodes by .value and then iterates over the snapshot and stores each child in an array as a FDataSnapshot. Then the code iterates over that array and prints the 'guardian' from each snapshot stored in the array.

I also included your code to print the guardianID and it works as well so my guess is the problem lies with how the array is being initially populated or in this line

for snapshot in self.guardians

as the snapshot is a NSFastEnumerationIterator

let ref = self.myRootRef.child(byAppendingPath: "guardian_node")!

ref.observe(.value, with: { snapshot in

     if ( snapshot!.value is NSNull ) {
          print("not found")
     } else {

          var guardianArray = [FDataSnapshot]()

          for child in snapshot!.children {
               let snap = child as! FDataSnapshot //downcast
               guardianArray.append(snap)
          }

          for child in guardianArray {
               let dict = child.value as! NSDictionary
               let thisGuardian = dict["guardian"]!
               print(thisGuardian)

               //your code
               let guardianID = (child.value as? NSDictionary)?["guardian"] as? NSString
               print(guardianID!)
          }
     }
})

*This is Swift 3 and Firebase 2.x but the concept is the same.

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