CODEWITHSUNDEEP
androidkotlin
Diego Perdomo
Diego Perdomo

Reputation: 463

Android val cannot be reassigned

I defined a variable called notes, when i try to modify it from a method, android studio says

val cannot be reassigned

however i can modify it if i access the variable like this: this.notes.

class NoteAdapter(var context : Context) : RecyclerView.Adapter<NoteViewHolder>(){

private var notes = emptyList<Note>()

override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): NoteViewHolder {
    var itemView = LayoutInflater.from(context).inflate(R.layout.note_item, parent, false)
    return NoteViewHolder(itemView)
}

override fun getItemCount(): Int {
    return notes.size
}

fun setNotes(notes: List<Note>) {
    this.notes = notes
    notifyDataSetChanged()
}

Why is this happening?

I come from a Javascript background so excuse my ignorance.

Upvotes: 4

Views: 13797

Answers (2)

Ankit Tale
Ankit Tale

Reputation: 2004

In Kotlin,

val - When you declared any variable in Koltin as final variable so once assigned we cannot changes the value of it.

So use var when you need to define/change value while running application

Upvotes: 3

CommonsWare
CommonsWare

Reputation: 1006799

You named two things notes:

private var notes = emptyList<Note>()

and:

fun setNotes(notes: List<Note>)

So, in the setNotes() function, notes refers to the function parameter. That is treated as a val and cannot be reassigned. this.notes refers to the notes property defined on your NoteAdapter class.

In general, try to use different names, to reduce confusion. For example, you might use:

fun setNotes(replacementNotes: List<Note>)

Upvotes: 13

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