Question

If I’m doing lots of pattern matching against a (relatively) complex case class, but most of the time I’m only interested in one or two of its fields. Is there a way to abstract away the other fields (perhaps by wrapping the class?)? Here’s an example of the type of thing I’m trying to simplify:

def receive = {
  case HttpRequest(POST, "foo", _, HttpBody(_, body), _) => // action
  case HttpRequest(GET, "bar", _, _, _) => // action
}

I’m only ever really interested in the request type, url and sometimes body so I would ideally like to define a pattern match as case Request(POST, "foo", body) or similar.

Answer 1

Just make your own Request extractor. Here’s a simplified example:

case class Complex(a: String, b: Int, c: String)
object Simple { 
  def unapply(c: Complex): Option[(String, Int)] = Some(c.a, c.b) 
}

Complex("B", 2, "x") match {
  case Simple("A", i) => println("found A, " + i)
  case Simple("B", i) => println("found B, " + i)
}

// prints "found B, 2"