CODEWITHSUNDEEP
scalainheritance
Sohaib
Sohaib

Reputation: 4694

Reuse variables in base class in derived class: Scala

Consider a code segment

trait MyTrait{
val x: Int = 0
}
case class MyClass(y: Int = 1, z: Int = 2) extends MyTrait
//script starts now
val myClass = MyClass(3,4)
myClass.copy(x, 5)

Why does this not work? It says undefined variable x. I know it can be written like 

case class MyClass(override val x:Int = 0, y: Int = 1, z: Int = 2) extends MyTrait

But I wish to know why can't I just use the default values?

EDIT

In such a scenario is it impossible to set MyTrait's x variable?

Upvotes: 0

Views: 166

Answers (2)

user3248346
user3248346

Reputation:

x is not in scope when you do myClass.copy(x, 5). You have defined x inside the trait but the x you have typed in the expression myClass.copy(x,5) is not that same x inside the trait. Hence the compiler complains about not finding the value x in myClass.copy(x,5).

Upvotes: 3

Jens Schauder
Jens Schauder

Reputation: 81950

There is no x, there is only a member x of the trait MyTrait (and of your class MyClass).

So this might do what you want:

myClass.copy(myClass.x, 5)

Upvotes: 1

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