3:37 a.m.
When I have the following rule:
rule "Discount Egypt"
salience 0
when
$T : TripRequest ( destination == "Egypt" )
then
((DiscountResult) $T.getResult()).setDiscount(5);
end
Is there a better way to do the 'then' part of the rule (when it comes to
formatting, but still executes the same thing)?
My request object has a result object that has a method called setDiscount
that needs to be called.
The setDiscount cannot be in the request object because there are multiple
kinds of Result Objects, thus the casting to its type.
This rule works fine, I was just wondering if there are any easier ways to
do it. I already found out you can do 'destination' instead of
'getDestination()' which helps make the rules more readable.
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3:46 a.m.
rule "Discount Egypt"
salience 0
when
$T : TripRequest ( destination == "Egypt" )
$dest: DiscountResult()
then
$dest=$T.getResult();
$dest.setDiscount(5);
end
On Wed, Apr 23, 2014 at 2:07 PM, Leonard93 <leonardlindenau(a)hotmail.com>wrote:
When I have the following rule:
rule "Discount Egypt"
salience 0
when
$T : TripRequest ( destination == "Egypt" )
then
((DiscountResult) $T.getResult()).setDiscount(5);
end
Is there a better way to do the 'then' part of the rule (when it comes to
formatting, but still executes the same thing)?
My request object has a result object that has a method called setDiscount
that needs to be called.
The setDiscount cannot be in the request object because there are multiple
kinds of Result Objects, thus the casting to its type.
This rule works fine, I was just wondering if there are any easier ways to
do it. I already found out you can do 'destination' instead of
'getDestination()' which helps make the rules more readable.
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5:41 a.m.
On 23/04/2014, Bharadwaj N <bharadwaj2012(a)gmail.com> wrote:
rule "Discount Egypt"
salience 0
when
$T : TripRequest ( destination == "Egypt" )
$dest: DiscountResult()
This is wrong: the rule will not fire unless there is a DiscountResult
fact in working memory.
then
$dest=$T.getResult();
This isn't correct either: you cannot assign to a bound variable.
$dest.setDiscount(5);
end
On Wed, Apr 23, 2014 at 2:07 PM, Leonard93
<leonardlindenau(a)hotmail.com>wrote:
> When I have the following rule:
>
> rule "Discount Egypt"
> salience 0
> when
> $T : TripRequest ( destination == "Egypt" )
> then
> ((DiscountResult) $T.getResult()).setDiscount(5);
> end
>
>
> Is there a better way to do the 'then' part of the rule (when it comes to
> formatting, but still executes the same thing)?
> My request object has a result object that has a method called
> setDiscount
> that needs to be called.
>
> The setDiscount cannot be in the request object because there are
> multiple
> kinds of Result Objects, thus the casting to its type.
>
> This rule works fine, I was just wondering if there are any easier ways
> to
> do it. I already found out you can do 'destination' instead of
> 'getDestination()' which helps make the rules more readable.
>
>
>
>
>
> --
> View this message in context:
>
http://drools.46999.n3.nabble.com/Is-there-a-better-way-to-write-this-rul...
> Sent from the Drools: User forum mailing list archive at Nabble.com.
> _______________________________________________
> rules-users mailing list
> rules-users(a)lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
>
6:17 a.m.
It only works if you do it like this:
rule "Discount Egypt"
salience 0
when
$T : TripRequest ( destination == "Egypt" )
$dest: DiscountResult()
then
$dest= (DiscountResult) $T.getResult();
$dest.setDiscount(5);
end
Since getResult() returns an instance of the interface IResult, it needs to
be cast to the proper type first. But this approach does not feel better
than the previous notation.
But thanks for the replies.
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2:15 p.m.
I think you missed Wolfgang's points.. this form is ***WRONG***
1) It assumes that the DiscountResult is in the working memory,
which may not be the case unless you insert it explicitly
2) it will fire for ANY DiscountResult/TripRequest combination
since there is no explicit join condition between the two.
3) Bound variables are not meant to be reassigned in the RHS.
4) Even the cast in the RHS will not save you from ClassCastExceptions,
unless it's implied that destinations "Egypt" can only have
DiscountResult as results.
You need something like this:
when
$T : TripRequest( destination == "Egypt",
$dest : result,
result#DiscountResult // same as
"instanceof"here
)
then
((DiscountResult) $dest).setDiscount( 5 );
end
One thing that could be done - but does not work right now,
is to expand on the "#" operator, so that whenever
you write
TripRequest( $dest : result#DiscountResult )
the variable $dest is created with DiscountResult as an
inferred type, rather than its declared type IResult
As mentioned, this does not work right now... it may
be a bug (cc-ing Mario for discussion)
Best
Davide
On 04/23/2014 04:17 AM, Leonard93 wrote:
It only works if you do it like this:
rule "Discount Egypt"
salience 0
when
$T : TripRequest ( destination == "Egypt" )
$dest: DiscountResult()
then
$dest= (DiscountResult) $T.getResult();
$dest.setDiscount(5);
end
Since getResult() returns an instance of the interface IResult, it needs to
be cast to the proper type first. But this approach does not feel better
than the previous notation.
But thanks for the replies.
--
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http://drools.46999.n3.nabble.com/Is-there-a-better-way-to-write-this-rul...
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3653
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3653
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4 comments
4 participants
participants (4)
-
Bharadwaj N -
Davide Sottara -
Leonard93 -
Wolfgang Laun