A-HA! Thank you! I figured I was making things overly complicated. :-) -Allen ________________________________ From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Edson Tirelli Sent: Friday, July 18, 2008 8:55 AM To: Rules Users List Subject: Re: [rules-users] Clarification of using collections as facts Hi all, sorry for the long absence. I'm back, but I know no one noticed, anyway... ;) Allen, not really. Collections usually are not asserted as standalone facts because they lack semantic meaning. They are abstractions, if you know what I mean. So, in your case, you can write patterns like this: Foo( names contains "abc" ) Foo( names not contains "abc" ) Now, a regexp will act over Strings, not collections. So if you want to write a rule that acts on each name that matches a regexp, you must "iterate" over your collections elements using the "from" CE: Foo( $names : names ) String( this matches "error.*" ) from $names Now, if you want the rule to re-create a new list containing only the names matching a pattern, THEN you may use the collect CE to create a collection: $foo : Foo( $names : names ) $foundThese : ArrayList( ) from collect( String( this matches "error.*" ) from $names ) You may also filter your resulting collection to only fire the rule when there are actual elements. Just for the sake of examples, since you are already binding $foo, you don't need to bind $names too: $foo : Foo( ) $foundThese : ArrayList( size > 0 ) from collect( String( this matches "error.*" ) from $foo.names ) Happy drooling, Edson 2008/7/15 Bagwell, Allen F <afbagwe@sandia.gov<mailto:afbagwe@sandia.gov>>: 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 _______________________________________________ rules-users mailing list rules-users@lists.jboss.org<mailto:rules-users@lists.jboss.org> https://lists.jboss.org/mailman/listinfo/rules-users -- Edson Tirelli JBoss Drools Core Development JBoss, a division of Red Hat @ www.jboss.com<http://www.jboss.com>