Matching Regular expressions

This topic is derived from the blog post: Using pattern matching with regular expressions in Scala

The Regex class in Scala provides a very handy feature that allows you to match against regular expressions. This makes dealing with certain types of regular expression very clean and easy to follow.

What needs to be done is to create a Regex class and assign it to a val. It is recommended that the val starts with an Uppercase letter, see the topic of matching about the assumptions matching makes based on the first letter of the Match case clause.

There is nothing like examples to help explain an idea:

1. // I normally use raw strings (""") for regular expressions so that I don't have to escape all \ characters
2. // There are two ways to create Regex objects.
3. // 1. Use the RichString's r method
4. // 2. Create it using the normal Regex constructor
5. scala> val Name = """(\w+)\s+(\w+)""".r
6. Name: scala.util.matching.Regex = (\w+)\s+(\w+)
8. scala> import scala.util.matching._
9. import scala.util.matching._
11. // Notice the val name starts with an upper case letter
12. scala> val Name = new Regex("""(\w+)\s+(\w+)""")
13. Name: scala.util.matching.Regex = (\w+)\s+(\w+)
15. scala> "Jesse Eichar" match {
16.      | case Name(first,last) => println("found: ", first, last)
17.      | case _ => println("oh no!")
18.      | }
19. (found: ,Jesse,Eichar)
21. scala> val FullName = """(\w+)\s+(\w+)\s+(\w+)""".r
22. FullName: scala.util.matching.Regex = (\w+)\s+(\w+)\s+(\w+)
24. // If you KNOW that the match will work you can assign it to a variable
25. // Only do this if you are sure the match will work otherwise you will get a MatchError
26. scala> val FullName(first, middle, last) = "Jesse Dale Eichar"
27. first: String = Jesse
28. middle: String = Dale
29. last: String = Eichar