Another option is to use implicit getters and setters.
public function get name( ):Datatype { } public function set name(value:Datatype):void { } package{ import flash.display.Sprite; public class Main extends Sprite{ public function Main(){ var counter: Counter = new Counter(); counter.count = 5; trace(counter.count); } } } class Counter { private var _count:uint; public function Counter( ) { _count = 0; } public function get count( ):uint { return _count; } public function set count(value:uint):void { if(value < 100) { _count = value; } else { throw Error( "Error" ); } } }