gistfile1.rb

class Profile < ActiveRecord::Base

  # ...

  def format_twitter_url
    unless self.twitter_url.blank? || self.twitter_url[/^https?:\/\//]
      if self.twitter_url[/twitter\.com/i]
        self.twitter_url = 'http://' + self.twitter_url
      else
        self.twitter_url = "https://twitter.com/#{self.twitter_url.sub(/@/, '')}"
      end
    end
  end
end