How can I serialize my User class for the Firebase Database and fix this error?

Question

I\'m trying to retrieve the updated User from the dataSnapshot of the Firebase Database:

mRef.addValueEventListener(new ValueEventListener() {
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Answer 1

For Kotlin, if you're using data class like below for firebase,

data class UserModel(
        var userName: String,
        var userType: Int
)

then you'll get an error like

com.google.firebase.database.DatabaseException: UserModel does not define a no-argument constructor. If you are using ProGuard, make sure these constructors are not stripped.

So for this, you just need to initialize its values.

data class UserModel(
        var userName: String = "",
        var userType: Int = 0
)