Scala method where type of second parameter equals part of generic type from first parameter

Question

I want to create a specific generic method in Scala. It takes two parameters. The first is of the type of a generic Java Interface (it's from the JPA criteria query). It currently looks like this:

def genericFind(attribute:SingularAttribute[Person, _], value:Object) {
  ...
}

// The Java Interface which is the type of the first parameter in my find-method:
public interface SingularAttribute<X, T> extends Attribute<X, T>, Bindable<T>

Now i want to achieve the following: value is currently of type java.lang.Object. But I want to make it more specific. Value has to be the of the same type as the placeholder "_" from the first parameter (and so represents the "T" in the Java interface).

Is that somehow possible, and how?

BTW Sorry for the stupid question title (any suggestions?)

EDIT: added an addtional example which could make the problem more clear:

// A practical example how the Scala method could be called 

// Java class:
public class Person_ {
  public static volatile SingularAttribute<Person, Long> id;
}

// Calling the method from Scala:
genericFind(Person_.id, Long)

Roswell

Answer 1

Of the top of my head (I'm still starting with Scala):

def genericFind[T](attribute:SingularAttribute[Person, T], value:T) {
  ...
}

Women

Wow, i'm deeply impressed ;) Thanks for the fast answer. Actually it seems to work. Scala rocks! BTW: not so important, but would that be also be possible in Java? – Roswell

Yes, it's possible in Java too, it would be the following: "public <T> Person genericFind( SingularAttribute< Person, T > attribute, T value ) { ... }". Hope this helps :). Note that there's some slight issues with this where, for example, you want to pass a subtype of T instead of an instance of exactly T. You can get around this with extra annotation but it's probably beyond what you need. – Drawing

Ok, good to know that its possible in Java. Don't need that extra annotation, but i would like to know which it is anyway! Thanks – Roswell

I omitted it because this form highlights badly but you want something like: public <T> Person genericFind( SingularAttribute< Person, ? super T > attribute, T value ) {...}. In Scala I think the equivalent is: def genericFind[T]( attribute: SingularAttribute[Person,_ <: T], value: T ). – Drawing

...although I should note that you would use variance in Scala if you controlled the "attribute" class, see here: scala-lang.org/node/129 – Drawing