Re: [rules-users] Use of helper class to simulate "accumulate"
Jeevan, sorry, I missed your e-mail in the limbo.
Just create a class or an attribute to be your accumulator...
For instance, if you create a "branchCounter" attribute in the Tree
object, you can do that:
rule "Count branches" salience 10
when
$t : Tree()
Branch( tree == $t )
then
$t.incrementBranchCounter();
modify( $t );
end
rule "Check branch count" salience 0
when
$t : Tree( branchCounter > 100 )
then
// do something
end
The only trick is the salience. The first rule must have a higher
salience in order to only fire the second rule after all branches are
counted.
Yes, in trunk you could do better with "accumulate" or "collect".
For
your case, "collect" would be simpler:
rule "Check branches"
when
$t : Tree()
$branches : ArrayList( size > 100 ) from collect( Branch( tree == $t ) )
then
// do something
end
[]s
Edson
Jeevan Tambuluri wrote:
Hello all,
I have been told that you could implement a helper class to simulate
"accumulate" command in drools. Could you please ealborate on how to
do this? Some code snippet to illustrate this would be very much
appreciated.
My problem is as follows.I have two types of facts - Tree and Branch.
Each Branch object has a reference to the Tree object it belongs to. I
want to write a rule: The number of branches in a tree must not
exceed 100. I guess this would be easy to write with "accumulate"
command, which is not yet available in 3.0.x.
Thanks
Jeevan
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Edson Tirelli
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