Things would be smpler if you could avoid re-creating Product objects
because adding an identical Object does not change the Set. (This
could be implemented with the help of a global Map<String,Product>,)
Second, overriding equals (and hashCode) in Product would also avoid adding
an "evil twin" in your rule code - as it is!
Even simpler is a solution where the relevant Product objects are inserted
as facts, so that
$cd1 : Product( name == "cd1" )
$bonus_cd : Product( name == "bonus_cd" )
$order : ShippingOrder( products contains $cd1, products not
contains $bonus_cd )
is true (again, with equals and hashCode being overridden).
Given your solution with collect, an additional eval testing for
"bonus_cd" not being the
name of the single Product in List $productList might be more
efficient than iterating
all products a second time.
-W
On 21 July 2010 00:41, javaj <jmilliro(a)ameritech.net> wrote:
I'm trying to write a rule to add an object to a collection if the collection
already contained a certain object with a specific attribute.
I developed a small example so maybe that will make more sense:
Use Case: In a product shipping applicaiton, anytime a product with the name
"cd1" is in the shipping order, a bonus product named "bonus_cd"
needs to be
added to the shipping order. The bonus cd should not be added if it's
already in the shipping order.
Shipping Order:
public class ShippingOrder {
private Set<Product> products;
public ShippingOrder() {}
public Set<Product> getProducts() {
return products;
}
public void setProducts(Set<Product> products) {
this.products = products;
}
}
Product:
public class Product {
private String name;
public Product(){}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
Rule:
rule "AddBonusCd"
when
$so : ShippingOrder()
$productList : ArrayList(size == 1) from collect( Product(name matches
"cd1|bonus_cd") from $so.products)
then
System.out.println("Adding Bonus Cd");
Set<Product> productSet = new
HashSet<Product>($so.getProducts());
Product bonusCd = new Product();
bonusCd.setName("bonus_cd");
productSet.add(bonusCd);
modify($so) {
setProducts(productSet);
}
end
The Shipping Order object is inserted as the fact.
The rule is valid if only cd1 or cd_bonus is in the shipping order. I only
want the rule to run when cd1 is in the product set but cd_bonus is not.
Makes sense?
Thanks,
J
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