From: Daniel Sheppard <daniels@...>
Date: 2007-11-01T11:33:36+09:00
Subject: Re: Extending ActiveRecord for csv export... a better way?

> As a new Ruby user (JRuby, actually), I've picked up this 
> language with
> a very specific purpose: to export data from a JDBC database into flat
> files.  I've figured out how to get the data out of the DB and into a
> file (using ActiveRecord-JDBC), but it requires a bit too much
> configuration.  My first stab implementation requires me to define an
> activerecord class for each table I want to export, and to define a
> method all_columns in each class
> that lays out the columns in the correct order.  I've also setup a
> module (CSVable) that extends ActiveRecord so I can call the export
> function directly on each class.  Here is the code:

require 'fastercsv'

def to_csv(records, filename=nil, columns=nil)
  filename ||= "#{records.first.class.table_name}.dat"
  columns ||= records.first.class.columns.map {|x| x.name }
  FasterCSV.open(filename, 'w') do |csv|
    records.each do |record|
      csv << columns.map {|column| record.attributes[column] }
    end
  end
end

class UsrUserAccount < ActiveRecord::Base
  set_table_name "USR.USER_ACCOUNT"
end

to_csv(UsrUserAccount.find(:all))