Re: [rules-users] using null in drools rulebase

Mike, The implicit connective constraint is AND, so if you write: when Beak(beak == "small beak", beak = null) You are saying: When beak is "small beak" AND beak is null... Which will always evaluate to false. []s Edson mike20043 wrote: >hi everyone > >need a bit more help here. im currently attempting to write some rules

>my rulesbase and can't seem to get the system to check if a variable is >empty. i have tried using null as shown in the code below > > >rule "small beak + small body + garden" > when > Beak(beak == "small beak", beak = null) && > Body(body == "small body") > Location(location == "garden") > then > ES.resultsmx("<p> ); > ES.resultsmx( Robin </p>"); > ES.resultsop(); >end > > > >which dosent work but for some reason i am able to check if it is not null >by doing this > > >rule "small beak + small body + garden" > when > Beak(beak == "small beak", beak != null) && > Body(body == "small body") > Location(location == "garden") > then > ES.resultsmx("<p> ); > ES.resultsmx( Robin </p>"); > ES.resultsop(); >end > > > >I have tired using == null but this returns a false and the rule dosent

>can anyone help me please. Also if anyone has any knowledge of how to

>rules so it only outputs one result instead of repeatedly running the >conditions and outputting results for each correct condition and also how

>check if a string variable contains a substring (within a rule) that would >be greatly appreciated . Thanks in advance > >mike > > -- Edson Tirelli Software Engineer - JBoss Rules Core Developer Office: +55 11 3124-6000 Mobile: +55 11 9218-4151 JBoss, a division of Red Hat @ www.jboss.com _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users