I can't remember but recently in one of the APIs I saw something like this class A (member:A){}. Scala does support it and there is no problem creating such a class but how do we initiate it and what purpose would such a class serve?

1 Answer 1


Something like var childNode = new Node(parentNode). You'd use it whenever you want a reference to anything of the same type. In this case, it might be reasonable to allow a null-valued parameter:

var root = new Node(null)
var child = new Node(root)
  • The class Node as per the need in question should expect a parameter of type Node or it's subclass, I don't think we can pass an instance of parent class to it. I tried it in REPL and it doesn't work. >>class C {def cfunc = println("cfunc")} >>class B (member:B) extends C {def bfunc = println("bfunc")} >>val c = new C() val b = new B(c) >><console>:10: error: type mismatch; found : C required: B val b = new B(c)
    – user116948
    Jan 31, 2014 at 0:07
  • There's no reference to parent/child classes in the question or in my answer. In my answer, the objects have a parent/child relationship, not the classes.
    – Paul Hicks
    Jan 31, 2014 at 0:57

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