CODEWITHSUNDEEP
scala
joesan
joesan

Reputation: 15435

Why can't I call asInstanceOf on an object in Scala?

Is there a way to do an asInstanceOf on a Scala object. Even though it is a singleton, it is still an instance. So why can't I do an asInstanceOf on this singleton?

Say:

case object MyObject

Upvotes: 2

Views: 221

Answers (2)

sjrd
sjrd

Reputation: 22105

You can, actually:

$ scala
Welcome to Scala version 2.10.0 (Java HotSpot(TM) 64-Bit Server VM, Java 1.6.0_39).
Type in expressions to have them evaluated.
Type :help for more information.

scala> case object MyObject
defined module MyObject

scala> val x: Any = MyObject
x: Any = MyObject

scala> x.asInstanceOf[MyObject.type]
res0: MyObject.type = MyObject

Upvotes: 3

elm
elm

Reputation: 20435

By definition a singleton (namely a Scala object) has one only instance, referred by the name used in the object declaration.

Also note that in a class you can refer to the type by the class name itself,

case class B()
val b = B()

b.isInstanceOf[B]
res: Boolean = true

However a case object proves to be a single instance; to refer to its type consider

case object A

A.isInstanceOf[A.type]
res: Boolean = true

Upvotes: 0

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