From: Allen <dba@...>
Date: 2005-09-14T04:08:24+09:00
Subject: Assigning to dynamic class attributes

Hi!

Ruby n00b here, but experienced in Perl and Python and many others, 
looking for guidance in my first program.

I want to build a class mirroring a flat file record that uses column 
names as accessor methods, I want to dynamically assign an attribute 
from a parsed string and assign it from the postitional list of symbols.

   rec = QlbRecord.new(file_line)
   rec.dpend += 5
   puts rec.address

First, I Set up the class attributes in the class.
   @@cols = [ :address, :classes, :status, :dpend, :cremote ]
   @@cols.each { |a| attr a,true }

Next, I would populate the fields as such....
     arec = record_string.split(/\t/)
     @@cols.each { |c| self.c = arec.shift }
where c is the sumbol of the attribute to set. This is wrong.

Am I going in the right direction? It is like using a hash
    data[c] = arec.shift
though I want to access the columns through methods (rec.address, etc.)

Is there a class in the library I should be using instead? Or do I 
really just need to replicate code (ick!) for each data field?
   address = arec.shift
   classes = arec.shift
   ... etc. ...

Also, I don't completely understand how symbols work or why they are 
needed.

Following is my class for your inspection. I can kludge something that 
works, but I want to learn the *best* method. Thanks!

########################
class QlbRecord
   @@cols = [ :address, :classes, :status, :dpend, :cremote ]
   @@cols.each { |a| attr a,true }

   def initialize(record_string=nil)
     from_s(record_string) if record_string
   end

   def from_s(record_string)
     arec = record_string.split(/\t/)
     @@cols.each { |c| self.c = arec.shift }
##---------------------> I want it to go to @address, @classes, etc
   end

   def to_s
     str=''
     @@cols.each { |c| str += (str>'' ? "\t" : '') + self.c }
##--------------------------------------------> from @address, etc.
     str
   end
end