How to override a mutable variable in Trait in scala?

Question

I\'d like override one mutable variable in Trait in constructor. But it will complain that \"overriding variable a in trait A of type Int; variable a cannot override a mutab

Answer 1

Overriding is only for methods. It doesn't make sense to override a variable. What changes if you override a variable with another variable of the same type? If anything, the value and that can just be set anytime anyway, because it is a variable:

trait A { 
  var a: Int = _ 
}

class B (a0: Int) extends A {
  a = a0
}

But that is propably not what you want. You may also just leave the getter and setter abstract:

trait A {
  def a: Int
  def a_=(value: Int): Unit
}

class B(var a: Int)

which is then equivalent to

trait A {
  var a: Int
}