Question

How to pass by-name repeated parameters in Scala?

The following code fails to work:

scala> def foo(s: (=> String)*) = {
<console>:1: error: no by-name parameter type allowed here
       def foo(s: (=> String)*) = {
                   ^

Is there any other way I could pass a variable number of by name parameters to the method?

Answer 1

This isn’t very pretty but it allows you to pass byname parameters varargs style

def printAndReturn(s: String) = {
  println(s)
  s
}

def foo(s: (Unit => String)*) {
  println("\nIn foo")
  s foreach {_()}  // Or whatever you want ...
}

foo()

foo((Unit) => printAndReturn("f1"),
    (Unit) => printAndReturn("f2"))

This produces

In foo

In foo
f1
f2