Hi,
I recently find out a few issues using for, and I wanted to share it with
you. I made a simple exemple to illustrate my purpose.
My classes are (I did not represent accessors & constructors):
public class Cheese {
protected String name;
}
public class FrenchCheese extends Cheese{
private String smell;
}
public class Person {
private Cheese likes;
}
Here is my rule set :
package rules
rule "likes cheese"
when
$person : Person ()
Cheese( ) from $person.getLikes()
then
System.out.println("likes cheese");
end
rule "likes french cheese"
when
$person : Person ()
FrenchCheese( ) from $person.getLikes()
then
System.out.println("likes french cheese");
end
First test :
Cheese cheese = new FrenchCheese("good", "camembert");
Person person = new Person();
person.setLikes(cheese);
Output :
likes french cheese
likes cheese
Wich is expected...
Second test :
Cheese cheese = new Cheese();
Person person = new Person();
person.setLikes(cheese);
Output :
likes french cheese
likes cheese
That's the first strange thing. As far as I am concerned, rule "likes french
cheese" should not match (since a Cheese is not a FrenchCheese).
I made a change to the second rule :
rule "likes french cheese"
when
$person : Person ()
FrenchCheese( smell == "good" ) from $person.getLikes()
then
System.out.println("likes french cheese");
end
Third test :
Cheese cheese = new Cheese();
Person person = new Person();
person.setLikes(cheese);
output :
It throwed an exception : Exception in thread "main"
java.lang.ClassCastException: rules.Cheese
I am not saying the ClassCastException is not to expect in such a case but I
think I would simply expect it not to match (as far as a Cheese is not a
FrenchCheese).
Chris
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