Scala - case classes inheriting types

Question

Is there a way to have a case class accept types defined in a trait that it mixes in? When I try what I would do with ordinary classes, it fails:

trait myTypes{ type aType = Array[String] } abstract class ParentClass extends myTypes{ //no issue here val a:aType = Array.fill[String](7)("Hello") } //error: not found: type aType case class ChildClass(arg:aType) extends ParentClass //error: not found: type aType case class ChildClass2(arg:aType) extends myTypes

Not sure why Scala would choose to behave this way, but I would appreciate some help in circumventing this annoying error.

J Cracknell · Accepted Answer · 2015-07-15 18:05:00Z

4

This happens because the type alias is out of scope:

// error: not found: type Bar class Foo(val bar: Bar) { type Bar = String }

Instead try:

class Foo(val bar: Foo#Bar) { type Bar = String }

answered Jul 15, 2015 at 18:05

J Cracknell

3,5471 gold badge22 silver badges13 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

User1291 Over a year ago

(commenting for the record:)this also works with inheritance: case class ChildClass(arg:ChildClass#aType) extends ParentClass.

J Cracknell Over a year ago

Yes, as the child class inherits both type and regular members of the parent.

Collectives™ on Stack Overflow

Scala - case classes inheriting types

1 Answer 1

2 Comments

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Related