16.9. Rule actions in DRL (THEN)

Use this to set the value of a field.

set<field> ( <value> )

$application.setApproved ( false );
$application.setExplanation( "has been bankrupt" );

Use this to specify fields to be modified for a fact and to notify the decision engine of the change. This method provides a structured approach to fact updates. It combines the update operation with setter calls to change object fields.

modify ( <fact-expression> ) {
    <expression>,
    <expression>,
    ...
}

modify( LoanApplication ) {
        setAmount( 100 ),
        setApproved ( true )
}

Use this to specify fields and the entire related fact to be updated and to notify the decision engine of the change. After a fact has changed, you must call update before changing another fact that might be affected by the updated values. To avoid this added step, use the modify method instead.

update ( <object, <handle> )  // Informs the decision engine that an object has changed

update ( <object> )  // Causes `KieSession` to search for a fact handle of the object

LoanApplication.setAmount( 100 );
update( LoanApplication );

Use this to insert a new fact into the working memory of the decision engine and to define resulting fields and values as needed for the fact.

insert( new <object> );

insert( new Applicant() );

Use this to insert a new fact logically into the decision engine. The decision engine is responsible for logical decisions on insertions and retractions of facts. After regular or stated insertions, facts must be retracted explicitly. After logical insertions, the facts that were inserted are automatically retracted when the conditions in the rules that inserted the facts are no longer true.

insertLogical( new <object> );

insertLogical( new Applicant() );

Use this to remove an object from the decision engine. The keyword retract is also supported in DRL and executes the same action, but delete is typically preferred in DRL code for consistency with the keyword insert.

delete( <object> );

delete( Applicant );