CODEWITHSUNDEEP
scala
user4298319
user4298319

Reputation: 432

Scala's sealed class "scope of seal"

I know that Scala allows to derive from sealed class if it is placed in the same file. May be there is a special construction or, if not, it makes sense to allow something like this:

sealed[Derived/*, list of allowed to derive*/] class Base
class Derived extends Base

This syntax will be like "Scope of protection":

class A{
  private[A] val value = 10
}

So it will allow to place Derived class to separate file.

Upvotes: 0

Views: 1612

Answers (1)

Mingyu
Mingyu

Reputation: 33359

A sealed class cannot have any new subclasses added except the ones in the same file.

Reasons for the design

1 - The programmers only need to worry about the subclasses they already know about.

2 - You get better compiler support because the compiler will flag missing combinations of pattern with a warning message.

Upvotes: 1

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