In Drools, can a selection clause (using keyword `from`) be written over an Iterable or Iterator?

Question

Given a Java interface like this:

class Hobby {
    public String getName() {...}
}

class Person {
    public Iterable<Hobby> getHobbies() {...}
}

How can I, in a LHS expression, select Hobby objects with a specific name. For example, something like this:

when
    $person: Person()
    $hobby: Hobby(name == "Knitting") from $person.hobbies

Is this supposed to work? It doesn't produce any results when we tried it.

Is there an alternative, given the Java code that returns an Iterable, rather than a Collection?

Answer 1

After fixing the mismatch person/$person, the rule compiles and fires if there is a person with "Knitting" in the hobbies collection. (Version 5.5, but I have no doubt that other versions work just as well.)

rule "who knits"
when
  $person: Person( $name: name )
  Hobby(name == "Knitting") from $person.hobbies
then
  System.out.println( "Knitting: " + $name );
end

public class Person {
  private String name;
  private List<Hobby> hobbies = new ArrayList<Hobby>();
  public String getName(){
    return name;
  }  
  public Iterable<Hobby> getHobbies(){
     return hobbies;
  }
}

Also, I don't see any Java interfaces in the snippets you've posted, just two classes.

If you have a problem, make sure to provide full code to reproduce the example.