Create a new object extending a trait and using early definition syntax

Question

How to create an objectthat extends a trait and uses early definition syntax?

Let's say we have two traits:

trait Trait {
  val value : String
}

trait Simple

Let's say we have also a simple class:

class Class

We can create a new object of type Class and make it extend a Simple trait:

new Class extends Simple

Is it possible to create a new object of type Class that extends the Trait and uses the early definition syntax to set value member? I tried something like:

     new Class  extends { override val value = "42" } with Trait

But this gives a syntax error:

Error:(12, 17) ';' expected but 'extends' found.
new Class extends { val value = "42" } with Trait

Can you clarify a bit more what you're trying to do? Why can't you just have this set up like a normal class? I suspect you want a lazy val, but can't find anything on the syntax you're referring to. — Ethan
– Ethan, Commented Aug 6, 2019 at 18:28
@Ethan Ooops, I meant early definition syntax. Actually, I have been just learning scala and just wondering, whether one can use that syntax when creating a new object. — lukeg
– lukeg, Commented Aug 6, 2019 at 18:31

Volty De Qua · Accepted Answer · 2019-08-06 21:29:01Z

0

trait T { val value: String }
class C
new C with T { val value = "ok" }

answered Aug 6, 2019 at 21:29

Volty De Qua

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2 Comments

atymic Over a year ago

Can you add some context around your answer?

Volty De Qua Over a year ago

@atymic The only "context around" that I would have been able to produce could have been "The right way to do that is ... ". But I was just afraid it would be just a redundant decoration on top of the implicit context determined by the question. I could have stated that using Class and Trait for class and trait names is a bad practice (readability and eventual collision), but it's about teaching. I like reading answers that explain complex things, but I prefer minimalist answers to minimal questions. Thanks though.

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