Case classes

Case classes are a special type of class that comes with several convenient definitions (equals, hashCode, toString, copy). There are two main uses:

1. Data object
2. Matching

First examples is using as a datastructure (Note: Some and None are both case classes):

1. scala> val tree = Node( "root",
2.      |                  Some(Node( "left", None, None)),
3.      |                  Some(Node( "right", None, Some( Node( "grandchild", None, None) ) ) )
4.      |                )
5. tree: Node = Node(root,Some(Node(left,None,None)),Some(Node(right,None,Some(Node(grandchild,None,None)))))
7. // you can deconstruct a datastructure made of cases classes
8. scala> tree match {
9.      | case Node( _, Some(left), Some(right) ) => println(left, right)
10.      | case _ => println( "shouldnt happen" )
11.      | }
12. (Node(left,None,None),Node(right,None,Some(Node(grandchild,None,None))))
14. scala> case class DataStructure( value1:String, value2:Int, value3:String)
15. defined class DataStructure
17. scala>  val d = DataStructure("one", 2, "three")
18. d: DataStructure = DataStructure(one,2,three)
20. scala> d.toString
21. res0: String = DataStructure(one,2,three)
23. scala> d == DataStructure("one", 2, "three")
24. res1: Boolean = true
26. scala> d == DataStructure("zero",1, "two")
27. res2: Boolean = false
29. scala> d.hashCode
30. res4: Int = 1652907895
32. // Only available in Scala 2.8
33. scala> d.copy( value3="newValue")
34. res5: DataStructure = DataStructure(one,2,newValue)