Laurent,
This could help....
=========
If you wanna test the parameters of the rules are different instances
of the same ObjectType you can use this:
If you have an Object:
public class MyObject{
private String name;
public MyObject(String name){
this.name=name;
}
public String getName(){
return this.name;
}
}
In your code you can have:
assertObject(new MyObject("o1");
assertObject(new MyObject("o2");
assertObject(new MyObject("o3");
assertObject(new MyObject("o4");
assertObject(new MyObject("o5");
In the DRL file you can have:
<java:functions>
public boolean diffInstances(Object obj1, Object obj2){
if (System.identityHashCode(obj1) >
System.identityHashCode(obj2)){
return true;
}
return false;
}
public boolean diffInstances(Object [] objects){
for (int i=0; i < objects.length-1;i++){
if (!diffInstances(objects[i],objects[i+1])){
return false;
}
}
return true;
}
</java:functions>
Then in your rule you can have something like this:
<rule name="test-different-instances" salience="1" no-loop="true">
<parameter identifier="o1">
<class>MyObject</class>
</parameter>
<parameter identifier="o2">
<class>MyObject</class>
</parameter>
<parameter identifier="o3">
<class>MyObject</class>
</parameter>
<parameter identifier="o4">
<class>MyObject</class>
</parameter>
<parameter identifier="o5">
<class>MyObject</class>
</parameter>
<java:condition>diffInstances(new
Object[]{o1,o2,o3,o4,o5})</java:condition>
<java:consequence>
System.out.println("o1:"+o1.getName());
System.out.println("o2:"+o2.getName());
System.out.println("o3:"+o3.getName());
System.out.println("o4:"+o4.getName());
System.out.println("o5:"+o5.getName());
</java:consequence>
</rule>
----
This will activate the rule just in 1 case when the instances are all
diferents.
========
Thursday, November 10, 2005, 7:50:18 PM, you wrote:
> Hi,
> I am new to drools, trying to see if I could use it to implement a
> discount engine.
> I am playing with the petstore example (shopping cart), and I was
> wondering if Drools has a pattern matching feature or not, if rules can
> be fired based on combinations rather than permutations.
> For example I want to implement a buy 2 Gold Fishes get 1 free discount.
> If I define my rule like:
> <java:condition>item1.getName().equals( "Gold Fish" )</java:condition>
> <java:condition>item2.getName().equals( "Gold Fish" )</java:condition>
> <java:consequence>
> //gives 100% discount to one item
> item2.setDiscount(100);
> </java:consequence>
> If the user puts 2 Golf Fishes in his cart (A, B), the rule will fire 4
> times (for permutation (A,A), (A,B), (B,B), (B, A), and gives 100%
> discount to all items...That does not work.
> I can add a condition to make sure the items are different and the rules
> fires only once per combo such as
> <java:condition>item1.getId()>item2.getId()</java:condition>
> That works in this case, but it is not scalable at all (if I want to do
> 4 gold fishes get 1 free...it gets more complicated).
> I also want the rule to fire more than 1 time if the user has let's say
> 8 gold fishes (he should get 4 free), so having a condition on the cart
> itself such as cart.hasXitems(4, "GolfFish") would probably not work I
> suppose (such rule would be fired only once if I understand how the
> engine works).
> So how would this (buy X items, get 1 free; applicable more than 1 time
> per cart) be implemented in a scalable and elegant way with drools?
> Is there some kind of pattern engine in drools (not sure if this is the
> proper term for this, but basically I want the rule to be fired only
> once per combination of facts that match some conditions, not per
> permutation..)?
> Thanks.
> Laurent
--------------------------
Felipe Piccolini
[EMAIL PROTECTED]
