Access function before calling superclass constructor in Kotlin data class

Another approach is to use companion object. This will allow you to call the function outside of the data class as well (maybe not useful in your particular case)

data class DataObject(val id: Int, val name: String) {

  constructor(context: Context, id: Int) : this(id, fetchName(context))

  companion object {

    fun fetchName(context: Context): String {
      val cursor = ...
      ...
      return name
    }
  }
}

You can only use member functions on a fully constructed objects. One way to work around that is to use private extension function or simply a function to fetch name:

private fun Context.fetchName(): String {
    ///...
    return cursor.getString(1)
}

data class DataObject(val id: Int, val name: String) {
    constructor(context: Context, id: Int) : this(id, context.fetchName())
}

Although I do think that using Cursor is a bit too heavy job for constructor. I'd use separate Factory like so:

data class DataObject(val id: Int, val name: String) {
    object FromCursorFactory {
        fun create(id: Int, context: Context): DataObject {
            val name = context.fetchName()
            return DataObject(id, name)
        }
    }
}

Further reading:

• Is doing a lot in constructors bad?
• Why is it considered bad practice to call a method from within a constructor?