How to pattern match large Scala case classes?

Question

Consider the following Scala case class:

case class WideLoad(a: String, b: Int, c: Float, d: ActorRef, e: Date)

Pattern matching allows me

Answer 1

You can always fall back to guards. It's not really nice, but better than normal pattern matching for you monster case classes :-P

case class Foo(a:Int, b:Int, c:String, d:java.util.Date)

def f(foo:Foo) = foo match {
  case fo:Foo if fo.c == "X" => println("found")
  case _ => println("arrgh!")
}

f(Foo(1,2,"C",new java.util.Date())) //--> arrgh!
f(Foo(1,2,"X",new java.util.Date())) //--> found

That said I think you should rethink your design. Probably you can logically group some parameters together using case classes, tuples, lists, sets or maps. Scala does support nested pattern matching:

case class Bar(a: Int, b:String)
case class Baz(c:java.util.Date, d:String)
case class Foo(bar:Bar, baz:Baz)

def f(foo:Foo) = foo match {
   case Foo(Bar(1,_),Baz(_,"X")) => println("found")
   case _ => println("arrgh!")
}

f(Foo(Bar(1,"c"),Baz(new java.util.Date, "X"))) //--> found
f(Foo(Bar(1,"c"),Baz(new java.util.Date, "Y"))) //--> arrgh!