From: new2ruby@... (New 2 Ruby)
Date: 2005-10-24T08:52:01+09:00
Subject: [SORT?] by x,y allowing x,y to be passed as parms

Question:  Are there better ways to do this
sort within the container class?

Have  class  CD with several fields defined,
@list_of_CDs array in class  CD_List holding CD pointers,
and a couple of methods to sort array of pointers by any two fields.

Below is relevant class entries and code.

class CD			      
  attr_reader :size, :cusip, :issuer,  :matures, ...
....
class CD_List 
  @@sortkey1= @@sortkey2 = "" 
  def initialize  @list_of_CDs = Array.new  end
  ...
  def new_ord(key1='size',key2='matures')       #Provide defaults
    @@sortkey1, @@sortkey2 = key1, key2	# Set  class variables
    @list_of_CDs.sort! { |a,b| cmp_item(a,b) }   # Sort in place
  end
  def cmp_item (a,b)	# Adapted from Ryan Pavlik
    # Allow different sort fields via Class variables
    f1 = eval('a.'+@@sortkey1) <=> eval('b.'+@@sortkey1)
    f2 = eval('a.'+@@sortkey2) <=> eval('b.'+@@sortkey2)
    (f1 == 0 ? f2 : f1) 
  end
....
listCD = CD_List.new		# Initialize it
....
listCD.new_ord('matures','cusip')	# Sort list of CDs
__END__

Complete script with test data (143 lines) at:
http://jmauney.freeshell.org/cgi-bin/data/CD_sort2.rb.txt
Comments on entire script also solicited.
 
Have searched this newsgroup, read FAQ at RubyCentral,
read HTML of Pickax ver. 1, and Googled without success.
Newest Pickax on order. 

Using ruby 1.8.2 (2004-12-25) [i386-mswin32]
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