How to filter by (child) domain class in Grails?
I have a parent domain class, Product:

    class Product {
        ...
    }

and more than 20 child classes extending it. One of this is ProductGroup:

    class ProductGroup extends Product {
        ...
    }

When creating an instance of ProductGroup, I have a multiselect input where products are listed and a user can select what products he/she wants to add to the group. Right now, I use Product.list() to populate the multiselect input. What I want to do is have a list of all products not including ProductGroup instances. What would be the best way to do this?
How to filter by (child) domain class in Grails?
===

I have a parent domain class, Product:

    class Product {
        ...
    }

and more than 20 child classes extending it. One of this is ProductGroup:

    class ProductGroup extends Product {
        ...
    }

When creating an instance of ProductGroup, I have a multiselect input where products are listed and a user can select what products he/she wants to add to the group. Right now, I use Product.list() to populate the multiselect input. What I want to do is have a list of all products not including ProductGroup instances. What would be the best way to do this?