Instantiating immutable paired objects
immutability, object, scala
Solution
Here is a complete solution to the Chicken/Egg problem:
class Chicken (e: =>Egg) {
lazy val offspring = e
}
class Egg (c: =>Chicken) {
lazy val mother = c
}
lazy val chicken: Chicken = new Chicken(egg)
lazy val egg: Egg = new Egg(chicken)
Note that you have to provide explicit types to the `chicken` and `egg` variables.
And for PairedObject:
class PairedObject (p: => PairedObject, val id: String) {
lazy val partner: PairedObject = p
}
lazy val p1: PairedObject = new PairedObject(p2, "P1")
lazy val p2: PairedObject = new PairedObject(p1, "P2")
Problem
Is it possible to create a class with an immutable reference to a partner object, or does it have to be a `var` that I assign after creation? e.g. ``` class PairedObject (p: PairedObject, id: String) { val partner: PairedObject = p // but I need ref to this object to create p! } ``` or similarly how could I instantiate the following pair? ``` class Chicken (e: Egg) { val offspring = e } class Egg (c: Chicken) { val mother = c } ```