Mastering High Performance with Kotlin

Backing properties

If you need to access a field of a property inside a class in which it's declared, you can use backing properties. If you only need to access a field from the getter or setter of its property, it's enough to use backing fields. However, if you want to access a field somewhere else, you should use backing properties. Let's look at the following example:

class Button {    private var _text: String? = null    var text: String        set(value) {            println(value)            _text = value        }        get() {            return _text + _text        }    fun printText() {        println(_text)    }}

In the preceding snippet, the _text variable is a field of the text property. To make sure of this, you can use the Kotlin Bytecode inspector:

public final class Button {   private String _text;   @NotNull ...