[rules-dev] declare LocalEvent @role( event ) end

[Wolfgang Laun]

I can declare a useful event type which doesn't have any fields
except the implicit timestamp and duration. As you've described,
the compiler assumes that this is an extension of an imported
fact, and complains if this cannot be found.

Here is a complete, not too contrived use case.

declare Trigger
  @role( event )
  @expires( 1s )
  void: Void         ## required due to compiler's insistence of
Trigger being defined elsewhere
end

rule "1m ticker"
    timer(int: 1m 1m)
when
then
    insert( new Trigger() );
end

rule "count jobs 30 minutes before Trigger"
when
    $t: Trigger()
    Number( $i: intValue > 3 ) from accumulate(
       Job( this before[0,30m] $t )
       count( 1 ) )
then
    retract( $t );
    System.out.println( "Too many jobs (" + $i + ") at " + clockAsString() );
end

Cheers
Wolfgang

On 10 November 2010 16:03, Edson Tirelli <tirelli at post.com> wrote:
>   Hi Wolfgang,
>
>   Not sure what is the intent with that?
>
>   Just to explain the design, the compiler differentiates two use
> cases: (1) if a declare has no fields in it, it understands the user
> is annotating an existing class. (2) If a declare has at least one
> field, then the compiler tries to generate a new class and annotate
> it.
>
>   In case (1) above, if the compiler does not find an existing class,
> it (correctly, IMO) raises an error.
>
>   Can you please clarify?
>
>   Thanks,
>       Edson
>
> 2010/11/10 Wolfgang Laun <wolfgang.laun at gmail.com>:
>> This simple declare for a new (not imported) class isn't permitted by
>> the compiler, although it makes sense.
>>
>> Of course, it's possible to work around by adding a dummy field.
>>
>> But is this restriction intentional by design, to alert users when
>> they misspell a class name, or forget to import a class?
>>
>> If not, I'll make a request to permit this.
>>
>> -W
>> _______________________________________________
>> rules-dev mailing list
>> rules-dev at lists.jboss.org
>> https://lists.jboss.org/mailman/listinfo/rules-dev
>>
>
>
>
> --
>   Edson Tirelli
>   JBoss Drools Core Development
>   JBoss by Red Hat @ www.jboss.com
>
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