ADOBE FLEX 3 183 Adobe Flex 3 Developer Guide // Do nothing, the constructor created the uid. } } } You do not need to use the UIDUtil class in a case where the objects contain a uniquely-identifying field such as an employee ID. In this case, you can use the person's ID as the uid property, because the uid property values uniquely identify the object only in the data provider. The following example implements this approach: package { import mx.core.IUID; [Bindable] public class Person implements IUID { public var employee_id:String; public var firstName:String; public var lastName:String; public function get uid(): String { return employee_id; } public function set uid(value: String): void { employee_id=value; } } } Note: Object cloning does not manage or have a relationship with UIDs, so if you clone something that has an internal UID you must also change that internal UID. UIDs are stored on mx_internal_uid only for dynamic Objects. Instances of data classes that implement IUID store their UIDs in a uid property, so that is the property that must be changed after cloning.