gistfile1.rb

 def self.guid_from_entry(entry)
    if entry.respond_to?(:guid) && entry.guid.present?
      Digest::MD5.hexdigest(entry.guid.to_s)
    elsif entry.respond_to?(:url) && entry.url.present?
      Digest::MD5.hexdigest(entry.url.to_s)
    elsif entry.respond_to?(:content) && entry.content.present?
      Digest::MD5.hexdigest(entry.content.to_s)
    else entry.respond_to?(:summary) && entry.summary.present?
      Digest::MD5.hexdigest(entry.summary.to_s)
    end
  end