It shouldn’t be hard to provide rewrite support for references to globals and the working memory methods – the logic to modify the methods would be the same
as for a rules defaultConsequence handler.
The main challenge then is to get the drools reference into the static functions.
The simplest solution could be to add the KnowledgeHelper in to a static ThreadLocal populated (and cleared) by either the rule or fireAllRules, the drl function
(or any other function) could then retrieve and use this.
Thomas
From: rules-users-bounces@lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org]
On Behalf Of Wolfgang Laun
Sent: 13 October 2010 18:45
To: Rules Users List
Subject: Re: [rules-users] DRL Functions
Implementing this would require a detailed parsing of function bodies and more,
to get the runtime object into the scope of the static methods compiled from
DRL functions.
As it is, a minor improvement is possible with:
import org.drools.spi.KnowledgeHelper;
function void ins( KnowledgeHelper kh, Object... obj ){
kh.insert( obj );
}
//...
then
ins( drools, new Fact( ... ) );
end
2010/10/13 Swindells, Thomas <TSwindells@nds.com>
I’ve just been writing what should be a really simple function in my DRL.
What I wanted to do is to take an object in, construct another object from it and then insert both into working memory.
Eg.
function
void insertBoth(Object1 object1) {
insert(new Object2(object1));
insert(object 1);
}
Rule XYZ
When
Then
insertBoth(new Object1());
End
This didn’t work as expected however as it couldn’t find the method insert.
I then thought, ah maybe I need to use the kcontext global to access them
function
void insertBoth(Object1 object1) {
kcontext.insert(new Object2(object1));
kcontext.insert(object 1);
}
Rule XYZ
When
Then
insertBoth(new Object1());
End
This doesn’t work either so what I’ve had to do is:
function
void insertBoth(KnowledgeContext kcontext, Object1 object1) {
kcontext.getKnowledgeRuntime().insert(new Object2(object1));
kcontext.getKnowledgeRuntime().insert(object 1);
}
Rule XYZ
When
Then
insertBoth(kcontext, new Object1());
End
This is suddenly a lot more complicated than it needs to be. Why can’t functions have the same access to the standard operations (insert, update, retract etc) and globals as rule
actions currently do?
Should I raise an issue for this or am I missing something?
Thomas
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