video_validator.rb

class VideoValiadtor < ActiveRecord::Validator
  def validate(record)
    # This regex will match YouTube and Vimeo videos
    regex = /^http:\/\/(?:.*?)\.?(youtube|vimeo)\.com\/watch\?[^#]*v=(\w+)|(\d+)/
    # Use it as follows:
    #
    #   "http://www.youtube.com/watch?v=AZDAIgwbXk4".match(regex)
    #   >> #<MatchData "http://www.youtube.com/watch?v=AZDAIgwbXk4" 1:"youtube" 2:"AZDAIgwbXk4" 3:nil>
    #
    #   "http://vimeo.com/60555406".match(regex)
    #   >> #<MatchData "http://vimeo.com/60555406" 1:"vimeo" 2:"60555406" 3:nil>
    #

    unless record.video_url.match(regex).nil?
      record.errors[:video_url] << "You have not provided a valid URL to video. Please, use YouTube or Vimeo."
    end
  end
end