Finding the difference between 2 ArrayCollections (like java?)

Question

Hi,
In java you can do a 'diff' between two Lists like this:  myList_new.removeAll(myList_old);  This removes from myList_new all the items identical in myList_old
Is there something similar in Actionscript or do I have to use brute force (loop thru both ArrayCollections and compare) ? My guess is that brute force is required since actionscript doesn't have generics but I'd love to be proved wrong !!!
thanks!

Answer 1

If your objects have a unique identifier on them you could do something like below.
Notice I use value.id as an assumption that "id" is the name of the identifier.  If you have a differently named identifer, you would need to change "id" to that name.
If there is no unique identifier on your objects, I think you'll just have to loop through the Collections and compare the attributes manually.
public function removeAll(collection1:ArrayCollection,
                    collection2:ArrayCollection):ArrayCollection{
  var dictionary : Dictionary = new Dictionary(true);
  var value : Object;
  var i:Number
  //Loop through first collection and put objects in dictionary
  for(i = 0; i < collection1.length; i++){
    value = collection1.getItemAt(i);
    dictionary[value.id] = value;
  //Loop through second collection and remove objects in dictionary
  for(i = 0; i < collection2.length; i++){
    value = collection2.getItemAt(i);
    if(dictionary[value.id] != null){
      delete dictionary[value.id];
  var unique:ArrayCollection = new ArrayCollection();
  //Loop through dictionary and put remaining value in collection
  for(var prop:String in dictionary){
    unique.addItem(dictionary[prop]);
  dictionary = null;
  return unique;