Let's write an extension to the String class:
Consider this code:
class String def vowels # from w w w. ja v a 2s. c o m self.scan(/[aeiou]/i) end end puts "This is a test".vowels.join('-')
Here, you've extended String with a vowels method.
The vowels method uses scan to return an array of all the vowels.
The i option on the end makes the regular expression case-insensitive.
We can put this code in a file called string_extensions.rb:
class String def vowels self.scan(/[aeiou]/i) end end
And put this code in a file called vowel_test.rb:
require 'string_extensions' puts "This is a test".vowels.join('-')
The first line, require 'string_extensions', loads in the string_extensions.rb file and processes it as if the code were local.