[rules-users] Problem passing objects to a method via the eval statement

[Joshua Undesser]

I am curious if anyone else has run into this problem.....It seems like there
is something wrong in the Drools Logic....My issue can be very easily be
recreated in about 5 minutes....

>From eclipse I set up a new drools project.    Where DroolTest.java is
defined I create 4 new classes,   ClassA, ClassB extends ClassA, ClassC
extends ClassA, and ClassD.

Each of these classes has a default constructor that does nothing, there are
no attributes or anything in these classes just to make the example simple
to reproduce.   Ie ClassA looks like this....



package com.sample;

public class ClassA {
	
	public ClassA() {
	}
}



Now within the DroolsTest.java source code at line 29 (ie right after the
workingMemory.insert( message ) method call I added 4 more lines which
creates and inserts two objects...

ClassB classB = new ClassB();
ClassD classD = new ClassD();
workingMemory.insert( classB );
workingMemory.insert( classD );

and then the next line would be the             
workingMemory.fireAllRules();   
as normal.


Then in the sample.drl file I add the following rule and functions

1 rule "Test"
2	 when
3
4		$classA : ClassA()
5		$classD : ClassD()
6	
7		(or
8			$classB : ClassB(eval($classB == $classA))
9			$classC : ClassC(eval($classC == $classA))
10		)	
11	
12		eval(retB($classA, $classD))	
13
14	then
15		System.out.println("\n\n<<FIRE RULE>>TEST");		
16 end		
17
18 function boolean retA(Object obj) {
19   System.out.println("Ret Val = " + obj);
20   return true;
21 }
22
23 function boolean retB(Object obj1, Object obj2) {
24	 System.out.println("Ret Val 1 = " + obj1);
25	 System.out.println("Ret Val 2 = " + obj2);
26	 return true;
27 }



So what I am doing is very quick and very simple to reproduce.   What is
happening is that when i run the program I am getting a class cast exception
which is very very strange.


At first I thought it was tied only to the OR statement because if I break
the rule into two rules (one for each of the or conditions) it works fine.

But after playing with it a little further I get a lot of other strange
class cast exceptions.

For instance if I replace line 12 (eval(retB($classA, $classD))) with
eval(retA($classA))  it works fine, but if I replace it with
eval(retA($classD)) I get another class cast exception.    Another strainge
issue....if switch lines 4 and 5 and keep line 12 as eval(retA($classD))
that previously failed, it now passes, but if I change line 12 back to
eval(retA($classA)) which previously passed it now fails.....

There are a few other combinations that produce errors as well.  Just seems
to be a fundamental flaw in the logic and I'm curious if anyone else has
seen this?

Thanks!

Joshua

P.S.

Also I've noticed an issue with the manual example 6.36 


This does not seem to work for me
	pensioner : (or Person( sex == "f", age > 60 ) 
                    Person( sex == "m", age > 65 ) )


But this does
(or pensioner : Person( sex == "f", age > 60 ) 
    pensioner : Person( sex == "m", age > 65 ) )




Although both formats are stated as working in the manual.






-- 
View this message in context: http://www.nabble.com/Problem-passing-objects-to-a-method-via-the-eval-statement-tp15885523p15885523.html
Sent from the drools - user mailing list archive at Nabble.com.