Basic Matching

Matching is a powerful concept in scala that is similar to a switch in Java. The difference is that matching takes it to another level. We will start with basic switching in this entry.

Note. If a match is not found a scala.MatchError is thrown

1. scala> val s = "sampleString"
2. s: java.lang.String = sampleString
4. scala> s match {
5.      | case "sampleString" => "its a match!"
6.      | case _ => "no match"
7.      | }
8. res0: java.lang.String = its a match!
10. scala> s match {
11.      | case m @ "sampleString" => "its a match!"
12.      | case _ => "no match"
13.      | }
14. res1: java.lang.String = its a match!
16. scala> s match {
17.      | case m @ "sampleString" => "we found "+m+"!"
18.      | case _ => "no match"
19.      | }
20. res2: java.lang.String = we found sampleString!
22. scala>  s match {
23.      | case m if(m.startsWith("s") ) => "its a match!"
24.      | case _ => "no match"
25.      | }
26. res3: java.lang.String = its a match!
28. scala>  s match {
29.      | case m => "this matches everything"
30.      | }
31. res4: java.lang.String = this matches everything
34. scala> val obj:Any = s // I am assigning s to a variable whose type is Any (parent of all object).
35. obj: Any = sampleString
37. scala>  obj match {
38.      | case string:String => "we found a string"
39.      | case integer:Int => "we found an integer"
40.      | case _ => "hmmm don't know what it is"
41.      | }
42. res6: java.lang.String = we found a string
44. scala> // Now  we will see what happens when a match fails
46. scala>  obj match {
47.      | case integer:Int => "we found an integer"
48.      | case double:Double => "we found an double"
49.      | }
50. scala.MatchError: sampleString
51.                   at .(:7)
52.                   at .()
53.                   at RequestResult$.(:3)
54.                   at RequestResult$.()
55.                   at RequestResult$result()
56.                   at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
57.                   at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
58.                   at sun.reflect.DelegatingMethodAccessorImpl.i...
59. scala>