just a quick question I seem to be unable to find an answer to.
I have a method definition in Scala that looks like this:
def execute(goals: List[String], profiles: List[String] = List(), loggingCallback: (String) => Unit = { _ => }): Result = { // method body loggingCallback("a message") }
I would like to know whether there is a better way to specify a default empty closure. The question is not about how to implement logging, this is just an example.
Answer
Your solution is fine. You could introduce a type alias for Function1[X, Unit]
; use ()
as per Kevin’s answer, and drop unnecessary parens.
scala> type Effect[-A] = (A => Unit)
defined type alias Effect
scala> def foo(f: Effect[String] = _ => ()) = ()
foo: (f: (String) => Unit)Unit
You could also define a noop
function:
scala> val noop = (a: Any) => ()
noop: (Any) => Unit = <function1>
scala> def foo(f: Effect[String] = noop) = ()
Attribution
Source : Link , Question Author : Andreas Eisele , Answer Author : retronym