On Mon, Aug 30, 2010 at 08:55:15PM -0700, Nathan Stults wrote:
>
> I am thoroughly enjoying your framework. I really like the way it is
> designed, easy to use, easy to extend. Anyway, I have a quick question
> regarding conditions.
Hello,
many thanks !
> What is the recommended approach to and'ing and
> or'ing expressions, like this (which doesn't seem to work)
>
> _if :test=>'${f:consent_form_on_file} == yes && ${f:is_patient_eligible}
> == yes' do
>
> Looking at the implementation of Condition I can see why what I'm trying
> to do isn't working, but I was wondering if there is some way? Is there
> a way to provide an array of conditions and an operator, or should I try
> to use nesting of flow expressions or something? I'm happy to use Ruby
> eval as well, but in that case I'm not sure how to get hold of work item
> variables. Can dollar syntax be used with ruby eval in expressions?
OK, I will answer in variants :
== decision participants
I tend to use "decision participants" like in
---8<---
sequence do
decide
_if "${f:decided}" do
accept
reject
end
end
--->8---
Where the 'decision participant' might look like
---8<---
class DecisionOne
include Ruote::LocalParticipant
def consume(workitem)
workitem.fields['decided'] =
workitem.fields['is_patient_eligible'] &&
workitem.fields['consent_form_on_file'] == 'yes'
reply_to_engine(workitem)
end
end
# ...
engine.register_participant 'decide', DecisionOne
--->8---
This makes the process definition more readable and lets you change the
decision logic independently from the business process.
That implies being able to hook more complex decisions (rule engine, decision
tables, your own complex decision library) or simply, sometimes, when the
decision is very very complex, switch from an automated participant to a human
participant (our dear friend the "knowledge worker").
== ruby evaluation
You can write :
---8<---
_if "${r:wi.fields[consent_form_on_file] == 'yes' &&
wi.fields['is_patient_eligible']}"
--->8---
Within the ${r: } you're free to use ruby code (and to shoot yourself in the
foot with it). There is a minimal sanity check (
http://github.com/jmettraux/ruote/blob/ruote2.1/lib/ruote/util/treechecker.rb )
but you have to have ruby evaluation allowed :
---8<---
engine.context['ruby_eval_allowed'] = true
--->8---
== hypothetical variant
Not a real variant : I have thought of things like
---8<---
sequence do
decide
_if do
_and do
test "${f:consent_form_on_file} == yes"
test "${f:is_patient_eligible}"
end
accept
reject
end
end
--->8---
but I never implemented it, preferring to guide people towards decision
participants or the ${r: } notation.
I hope this will help, best regards,
--
John Mettraux - http://jmettraux.wordpress.com
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