A type class providing evidence for parsing type T as a flag value.

Any class that is to be provided as a flaggable value must have an accompanying implicit Flaggable (contained within a companion object of the class in question) for converting a string to an object of that type. For instance, to make a hypothetical type called Foo flaggable:

class Foo {
  ...
}

object Foo {
  implicit val flagOfFoo = new Flaggable[Foo] {
    def parse(v: String): Foo = {
      ...
    }
  }
}

For simple implicit definitions based on existing String => T functions, use the Flaggable.mandatory function:

object Foo {
  def parse(v: String): Foo = {
     ...
  }

  implicit val ofFoo = Flaggable.mandatory(Foo.parse(_))
}

[1] https://en.wikipedia.org/wiki/Type_class