Question 118903 in Firebase Question posted in
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Retrieve/get nested node objects from firebase realtime using kotlin

I want to get the data objects (address, check_in, check_out) from the date which is in the nested node.

My database goes by like this:


---`attendance` :{
   |
   |---danielle:{ <---------- here is username, node of `attendance`
   |   |
   |   |---2023-04-08: <----------- here is the date she checked in and out for work
   |   |   |
   |   |   |---address: "Thomas street"
   |   |   |
   |   |   |---check_in: "09:02 AM"
   |   |   |
   |   |   |---check_out: "06:30 PM"
   |   |
   |   |
   |    ---2023-04-10":
   |       |
   |       |---address: "Maria street"
   |       |
   |       |---check_in: "09:02 AM"
   |       |
   |        ---check_out: "06:30 PM"
   |
    ---mark:{ <---------- here is another username
       |
       |---2023-04-07: <----------- here is the date he checked in and out for work
       |   |
       |   |---address: "Thomas street"
       |   |
       |   |---check_in: "09:02 AM"
       |   |
       |   |---check_out: "06:30 PM"
       |
       |
        ---2023-04-11":
           |
           |---address: "Maria street"
           |
           |---check_in: "10:23 AM"
           |
            ---check_out: "08:30 PM"

I tried to use this coding

val attModel = arrayListOf<AttendanceModel>()

Firebase.database.getReference("Attendance").child("danielle").child("2023-04-08").addValueEventListener(object : ValueEventListener {
                override fun onDataChange(snapshot: DataSnapshot) {
                    for (h in snapshot.children) {
                        val data = h.getValue(AttendanceModel::class.java)

                        attModel.add(data!!)

                    }
                }
            }

but i get this error

Android : com.google.firebase.database.DatabaseException: Can't convert object of type java.lang.String to AttendanceModel

I know danielle is indeed a String, but I don’t understand how it can get an error because danielle has an object node inside.

I also tried this coding here where I tried to nest for the path 2023-04-08

val todays = arrayListOf<AttendanceModel>()

        Firebase.database.getReference("Attendance").child("danielle")
            .addValueEventListener(object : ValueEventListener {
                override fun onDataChange(snapshot: DataSnapshot) {
                    for (h in snapshot.children) {
                        val date = h.child("2023-04-08")
                        for (i in date.children) {
                            val dataUser = i.getValue(AttendanceModel::class.java)

                            todays.add(dataUser!!)
                        }

In emulator doesnt return anything, and then i tried to log dataUser, it gives me

DataSnapshot { key = danielle, value = null }

Here is my data class

data class AttendanceModel(
    val loc_name: String? = "",
    val address: String? = "",
    val check_in: String? = "",
    val check_out: String? = ""
)

Any kind of help would be so much appreciated!

Tags:

2

Answers


  1. 0

    No need iteration snapshot children because already entire object fetch for date. If we use iteration, it’s will return value for each key which inside the object.

    Replace

    for (h in snapshot.children) {
val data = h.getValue(AttendanceModel::class.java)
 attModel.add(data!!)
 }

    by

     val data = snapshot.getValue(AttendanceModel::class.java)
            attModel.add(data!!)
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  2. 0

    When you attach a listener on the 2023-04-08, there is no need for an iteration, you can directly read the values of the children, or you can map the node into an object of type AttendanceModel. In code, it will be as simple as:

    val db = Firebase.database.reference
val dateRef = db.child("attendance/danielle/2023-04-08")
dateRef.get().addOnCompleteListener {
    if (it.isSuccessful) {
        val snapshot = it.result
        val key = snapshot.key
        Log.d(TAG, "key: $key")
        val data = snapshot.getValue(AttendanceModel::class.java)
        Log.d(TAG, "data: ${data.address}${data.check_in}/${data.check_out}")
    } else {
        Log.d(TAG, "${it.exception?.message}") //Never ignore potential errors!
    }
}

    The result in the logcat will be:

    key: 2023-04-08
data: Thomas street/09:02 AM/06:30 PM
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