[rules-users] determining what field changed

[Greg Barton]

Not really.  Without modifying the objects you could do this outside the rules using a WorkingMemoryEventListener, which has objectInserted() and objectUpdated() methods.  Event if you can modify the DataObject to add an "I'm a new object" flag, and set it immediately on insertion, then you could do differentiate with two rules:

rule "identify new DATAOBJECT" 
when 
      do : DataObject(n00b == true); 
then    
  do.setN00b(false);
  update(do);
  System.err.println("DataObject assertion detected: " + do);
end 

rule "identify modified DATAOBJECT" 
when 
      do : DataObject(n00b == false); 
then    
  System.err.println("DataObject modification detected: " + do);
end 

Which would still catch a spurious modification notification on assert!  At that point the semi-risky alternative is to not call update() in the "identify new DATAOBJECT" rule action.  That way, the "identify modified DATAOBJECT" is not immediately activated, but it would be activated the next time update() is called on the object.  I say semi-risky because it's not often a good idea to put a WM object into a state that the rete is not aware of, but in this case it would do what you want.

--- On Wed, 9/16/09, Chris Richmond <crichmond at referentia.com> wrote:

> From: Chris Richmond <crichmond at referentia.com>
> Subject: [rules-users] determining what field changed
> To: "'Rules Users List'" <rules-users at lists.jboss.org>
> Date: Wednesday, September 16, 2009, 2:41 PM
> 
> Is it possible
> to determine what fields from an object
> changed within a rule.   
> 
> So I am using
> this to determine if any DataObject has
> changed:  
> 
> //IDENTIFY ANY DATAOBJECT
> CHANGES 
> 
> rule
> "identify any DATAOBJECT" 
> when 
>       $do :
> DataObject(); 
> then    
> System.err.println("ANY
> DataObject change detected:" + $do);
> End 
> 
> However this
> also fires when any new DataObject() is
> injected into the system and the rules are fired.  I
> would like to be able to
> only have a rule fire when  an object is first
> created 
> 
> Vs. when it is
> modified and is there a way to detect what
> values of an object have changed if I don’t
> explicitly know what fields
> of DataObject changed ahead of time? 
> 
> Thanks,
> Chris 
> 
> -----Inline Attachment Follows-----
> 
> _______________________________________________
> rules-users mailing list
> rules-users at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
>