justRIA

Actually, not that harmful. But you should be aware of a special meaning of this Flex object property. Here’s the story:

Today, I tried to develop a method the create shallow and deep copies of objects. Finally, I prepared this method, initially without the line marked with __MARK__:

static private function clone( source:Object, deep:Boolean = false ):Object
  {
    if ( null == source ) {
    return null;
    }
    var copy:Object;
    if ( true == deep ) {
       copy =  ObjectUtil.copy( source );
    } else {
      copy = new Object();
      for( var key:Object in source ) {
        if (  ( 'mx_internal_uid' != key ) ) {     // __MARK__
          copy[ key ] = source[ key ];
        }
     }
  }
  return copy;
} // clone

Without the line marked by __MARK__, the method copies (more or less raw) objects, but the dataProvider-driven controls gets in trouble: List-based control add each managed object a ‘mx_internal_uid‘ to identify each data object. Thus, if you copy the ‘mx_internal_uid’ property, e.g. a DataGrid will no longer be able to distinguish the original source object or the clone(source) object.

Thus, it’s appropriate to not copy ‘mx_internal_uid‘ from source to clone.