Kotlinmedium

Delegated properties (`by`): what problem do they solve?

Answer

Delegated properties let you reuse getter/setter logic (lazy initialization, observable changes, validation) without boilerplate. You delegate the property to another object that provides `getValue`/`setValue`.

var name: String by Delegates.observable("<init>") { _, old, new ->
  println("$old -> $new")
}

name = "Ala"

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