CODEWITHSUNDEEP
scalagenericsshapeless
Ben
Ben

Reputation: 25

Getting name of parameterized class in scala using shapeless

I want to get the name of a class passed as a parameter to a function using shapeless. I've tried this: 

def sayMyName[T](t: T): String = Typeable[T].describe // error: class type required but T found

If T is replaced with a concrete type, there's no problem. Is it possible to make something like this work using shapeless?

Upvotes: 1

Views: 107

Answers (1)

Krzysztof Atłasik
Krzysztof Atłasik

Reputation: 22595

You just need to add Typeable typeclass as context bound of your type T:

def sayMyName[T: Typeable](t: T): String = Typeable[T].describe

sayMyName("") //String

You could also explicitly declare implicit parameter:

def sayMyName[T](t: T)(implicit typeable: Typeable[T]): String = Typeable[T].describe

By adding context bound you're asking the compiler to wait with resolving Typeable
typeclass until sayMyName is called with the concrete type, not resolve it right away (which is impossible, since the real type of T is not yet known at this point).

Upvotes: 1

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