def eachField( record = @record )
      if record and block_given?
         record.each{ |field|
             if field.is_a?( REXML::Element) and field.name == "f" and field.attributes["id"]
                @field = field
                yield field
             end
         }
      end
      nil      
   end
def eachField( record = @record )
      if record and block_given?
         record.each{ |field|
             if field.is_a?( REXML::Element) and field.name == "f" and field.attributes["id"]
                @field = field
                yield field
             end
         }
      end
      nil      
   end
Iterate record XML and yield only 'f' elements.