How to avoid KotlinNullPointerException when creating a new User object?

Question

I have this authentication code in Firebase:

auth.signInWithCredential(credential).addOnCompleteListener { task ->
    if (task.isSuccessful) {
        val firebaseUser = auth.currentUser!!
        val user = User(firebaseUser.uid, firebaseUser.displayName!!) //KotlinNullPointerException
    } 
}

This my User class:

data class User constructor(var uid: String? = null): Serializable {
    var name: String? = null

    constructor(uid: String, name: String) : this(uid) {
        this.name = name
    }
}

And I'm getting a KotlinNullPointerException at the highlighted line. How can the call of the constructor produce this exception? How can I avoid it?

Answer 1

Just declare your class like:

data class User(var uid: String? = null, var name: String? = null) : Serializable

And then you can call it like:

auth.signInWithCredential(credential).addOnCompleteListener { task ->
    if (task.isSuccessful) {
        auth.currentUser?.apply {  // safe call operator, calls given block when currentUser is not null
            val user = User(uid, displayName)
        }
    } 
}

It is possible to create instance of User like this:

User() // defaults to null as specified
User("id") // only id is set, name is null
User(name = "test-name") // only name is set id is null

The = null exactly allows the invokation to pass the parameter optionally, when not passed defaulting to null.

Edit: As suggested by @GastónSaillén, you should use Parcelable in Android.

@Parcelize
data class User(var uid: String? = null, var name: String? = null) : Parcelable