From: Brad Phelan <phelan@...>
Date: 2006-12-20T01:30:06+09:00
Subject: Re: ruby puzzle: Group candies by unique record fields

Woga Swoga wrote:
> I have an list of objects (Candy) and each object has two fields
> (Candy.color, Candy.taste).  I would like to display the candies but
> group them based on the fields (display a header for each group).  The
> problem is I don't know how many colors or tastes are in any particular
> list of candies.
> 
> This is what I have for input:
> 
> * Candy  <-- hash list already pre-sorted by "group"
> * group  <-- variable contains either "color" or "taste"
> 
> Can anyone come up with a ruby code snipet that will use the "group"
> variable to extract out the group labels (unique values of the color or
> tate field), and then dump out the Candy list by group.
> 
> Really appreciate your help!
> 

require 'yaml'

@candies = [
     { :name => 'a', :color => "blue", :taste => "good" },
     { :name => 'b',:color => "blue", :taste => "yuck" },
     { :name => 'c',:color => "red", :taste => "ok" },
     { :name => 'd',:color => "blue", :taste => "yuck" },
     { :name => 'e',:color => "green", :taste => "good" },
     { :name => 'f',:color => "green", :taste => "yuck" }
]

def print_candies_by(group)
     groups={}
     @candies.each do |candy|
         key = candy[group]
         groups[key] = [] unless groups[key]
         groups[key] << candy
     end

     puts "##########'"
     puts YAML.dump groups
     puts "##########'"
end


print_candies_by :taste
print_candies_by :color

----------------
##########'
---
good:
- :taste: good
   :name: a
   :color: blue
- :taste: good
   :name: e
   :color: green
yuck:
- :taste: yuck
   :name: b
   :color: blue
- :taste: yuck
   :name: d
   :color: blue
- :taste: yuck
   :name: f
   :color: green
ok:
- :taste: ok
   :name: c
   :color: red
##########'
##########'
---
green:
- :taste: good
   :name: e
   :color: green
- :taste: yuck
   :name: f
   :color: green
blue:
- :taste: good
   :name: a
   :color: blue
- :taste: yuck
   :name: b
   :color: blue
- :taste: yuck
   :name: d
   :color: blue
red:
- :taste: ok
   :name: c
   :color: red
##########'


--
Brad Phelan
http://xtargets.com