Kotlin: Unresolved reference to member function Intellisense suggests?

Question

I am learning kotlin in android studio, and I must be making a syntax error.

I have the class:

abstract class RoomDB : RoomDatabase() {
   fun getInstance(context:Context) : RoomDB {
       // either finds an existing database or makes a new one
       // returns the database
   }
}

Later I am writing the following code:

import android.example.app.Database.RoomDB

class MainActivity : AppCompatActivity() {
    lateinit var database:RoomDB

    override fun onCreate(savedInstanceState: Bundle?) {
        database = RoomDB.getInstance(this)
    }
}

Autocomplete suggests the getInstance method; however, when I write this code, I get an unresolved reference error to this method. Any idea why?

Answer 1

At the suggestion of Slaw I put the method declaration inside of a companion object which fixed the compile errors. I do not understand why that fixed this.

abstract class RoomDB : RoomDatabase() {
   companion object {
      fun getInstance(context:Context) : RoomDB {
          // either finds an existing database or makes a new one
          // returns the database
      }
   }
}