From: Jeffrey Schwab <jeff@...>
Date: 2006-03-16T23:38:47+09:00
Subject: Re: csv nil check and update

Geoff wrote:

> require 'CSV'
> 
> last = ""
> newFile = File.open("C:\\temp\\geoff\\filldown\\filldownNew.txt", "w+")
> CSV.foreach("C:\\temp\\geoff\\filldown\\filldown.txt") do |row|
> 	if row[-1].empty?
> 		row[-1] = last
> 	else
> 		last = row[-1]
> 	end
> 	newFile << (p row)
> end

Do you need to preserve the redundant quotes in the output?  If not, 
this might be what you want:

     # vim:ts=4 sw=4 et
     require 'CSV'

     last = ''
     out_csv = CSV.open('output.csv', 'w')
     CSV.foreach('input.csv') do |row|
         if row[-1].empty?
             row[-1] = last
         else
             last = row[-1]
         end
         out_csv << row
     end
     out_csv.close

If it were me, I would probably group the datum "last" and the 
functionality that dealt with it into a separate object, at the expense 
of longer code.  Maybe it's premature factoring, but I can just see that 
loop body getting more complicated as you want to do more with it, like 
replacing all blank fields (instead of just the last one) with 
previously read values.

     # vim:ts=4 sw=4 et
     require 'CSV'

     class BlankFiller
         def initialize(last='')
             @last = last
         end

         def fill(e)
             if e.empty?
                 e = @last
             else
                 @last = e
             end
         end
     end

     blank_filler = BlankFiller.new
     out_csv = CSV.open('output.csv', 'w')
     CSV.foreach('input.csv') do |row|
         row[-1] = blank_filler.fill(row[-1])
         out_csv << row
     end
     out_csv.close