place_submission.rb

      self.guid = Digest::SHA2.new.tap do |d|
        d << (self.name || "NULL")
        d << (self.key || "NULL")
        d << (self.infogroup_id || "NULL")
        d << (self.street || "NULL")
        d << (self.city || "NULL" )
        d << (self.state || "NULL")
      end

How about:

self.guid = Digest::SHA2.new.tap do |d|
  %w(name key infogroup_id street city state).each do |field|
    d << (send(field) || "NULL")
  end
end

Digest::SHA2.hexdigest attributes.values_at('name', 'key', 'infogroup_id', 'street', 'city', 'state').to_json

Eric's answer is more complete. What I pasted is what we do in place_directory, which you'll see in a few files called identity.rb