What is the Scala equivalent to a Java builder pattern?

Question

In the work that I do on a day to day in Java, I use builders quite a lot for fluent interfaces, e.g.: new PizzaBuilder(Size.Large).onTopOf(Base.Cheesy).with(Ingredien

Answer 1

Another alternative to the Builder pattern in Scala 2.8 is to use immutable case classes with default arguments and named parameters. Its a little different but the effect is smart defaults, all values specified and things only specified once with syntax checking...

The following uses Strings for the values for brevity/speed...

scala> case class Pizza(ingredients: Traversable[String], base: String = "Normal", topping: String = "Mozzarella")
defined class Pizza

scala> val p1 = Pizza(Seq("Ham", "Mushroom"))                                                                     
p1: Pizza = Pizza(List(Ham, Mushroom),Normal,Mozzarella)

scala> val p2 = Pizza(Seq("Mushroom"), topping = "Edam")                               
p2: Pizza = Pizza(List(Mushroom),Normal,Edam)

scala> val p3 = Pizza(Seq("Ham", "Pineapple"), topping = "Edam", base = "Small")       
p3: Pizza = Pizza(List(Ham, Pineapple),Small,Edam)

You can then also use existing immutable instances as kinda builders too...

scala> val lp2 = p3.copy(base = "Large")
lp2: Pizza = Pizza(List(Ham, Pineapple),Large,Edam)