[rules-users] Clarification of using collections as facts

[Bagwell, Allen F]

I'm going through the Drools documentation regarding the use of lists and other collections. I want to make sure my understanding is correct.

So if I have a class:

public class Foo {

   private int x;
   private int y;
   private List<String> names = ArrayList<String>();

   public List<String> getNames() {return names;}

   // appropriate getters/setters for the int fields ...
}

With this I can insert a Foo object into working memory. I can even make the int fields dynamic facts with the appropriate addition of "bean-ifying" code.

For the List, however, I need to insert it separately into working memory in order to make use of Drools' rule language ('contains' ,etc.)? I'm assuming that doesn't come free because I have to insert my own custom class objects if they are included via composition in a larger fact!

Also, I'm guessing the Collection type classes cannot be dynamic facts? Meaning if I modify my List with add, remove,  clear, etc., I must explicitly call update in my code on the List fact in order to alert Drools to a change in the List, correct?

So then the question also comes up as to how I would write a rule that looks for all instances of Strings in the List that match against a given regex expression. I've not been successful at figuring this out...

Rule "when a Foo List is modified, get all Strings in it that start with 'error'"
when
   $foo : Foo($names : names)
   $foundThese : ArrayList() from collect(??? matches "error.*" from $names)
then
   // act on $foo and $foundThese

I know that rule is NOT correct, but I'm not sure how I'm supposed to access an immutable object inside a collection. The examples in the documentation show how to get at mutable class objects.


Thanks!
-Allen
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.jboss.org/pipermail/rules-users/attachments/20080715/a9771d64/attachment.html