parse_video_id.rb

module RubyBBCode

  def self.parse_youtube_id(url)
    #url = "http://www.youtube.com/watch?v=E4Fbk52Mk1w"
    url =~ /[vV]=([^&]*)/
    
    id = $1
    
    
    if id.nil?
      # when there is no match for v=blah, then maybe they just 
      # provided us with the ID the way the system used to work... 
      # e.g. "E4Fbk52Mk1w"
      return url  
    else
      # else we got a match for an id and we can return that ID as a string...
      return id
    end
  end
  
end

test.rb

def test_youtube_parser
    url1 = "http://www.youtube.com/watch?v=E4Fbk52Mk1w"
    just_an_id = 'E4Fbk52Mk1w'
    url_without_http = "www.youtube.com/watch?v=E4Fbk52Mk1w"
    url_without_www = "youtube.com/watch?v=E4Fbk52Mk1w"
    url_with_feature = "http://www.youtube.com/watch?feature=player_embedded&v=E4Fbk52Mk1w"
    
    expected_output = 'E4Fbk52Mk1w'
    
    assert_equal expected_output, 
                   RubyBBCode.parse_youtube_id(url1)
    
    assert_equal expected_output, 
                   RubyBBCode.parse_youtube_id(just_an_id)
                   
    assert_equal expected_output, 
                   RubyBBCode.parse_youtube_id(url_without_http)
                   
    assert_equal expected_output, 
                   RubyBBCode.parse_youtube_id(url_without_www)
                   
    assert_equal expected_output, 
                   RubyBBCode.parse_youtube_id(url_with_feature)
    
  end