I want to get actual type class from Generic type.
When I try this
I get class scala.runtime.Nothing only.
import scala.reflect._ class Car { } object Car extends Model[Car] { } trait Model[T] { def something[T:ClassTag]():Unit = { println(classTag[T].runtimeClass) } } Car.something() // <- scala.runtime.Nothing$ You might want something like the following: The T=:=U would unify the two types and the :ClassTag would just create a ClassTag for it.
Edit: the correct, but still too complicated form:
trait Model[T] { def something[U](implicit ev: T =:= U, tag: ClassTag[U]): Unit = { println(tag.runtimeClass) } In general, I would also use https://stackoverflow.com/a/27666845/1502148 (when I am not sleepy :) ).
def something[U](implicit ev: T =:= U, tag: ClassTag[U]).class Model[T:ClassTag] { def something():Unit = { println(classTag[T].runtimeClass) } } I solved by modifying Model trait to class and provide ClassTag to Generic.
If you want to allow creating a Model without ClassTag and only require ClassTag for some methods, you can do
trait Model[T] { def something(implicit tag: ClassTag[T]):Unit = ... } Obviously this applies to e.g. Numeric, Ordering, etc. constraints as well.
Ts are different. Try:Car.something[String]()for example.