From: Ashley Moran <work@...>
Date: 2006-06-23T03:50:59+09:00
Subject: Turning an Array into a Hash based on an attribute value

A guy I work with has some some work on an ActiveRecord class that  
basically reads static lookup data, and contains (among other things)  
an "identifier" attribute.  Given an array of all these objects he  
wanted to access them by the contents of the identifier attribute, eg:

data_items = DataItem.find(:all)
# data_items[3].identifier => "my_identifier"
data_items[:my_identifier].do_something # => data_items[3].do_something

The best I can come up with is this:

   class Array
     def hash_on(method)
       method = method.to_sym
       hash = { }
       self.each do |i|
         hash[i.send(method).to_s.to_sym] = i
       end
       hash
     end
   end

   > [1, "2", :three].hash_on(:class)
   => {:String=>"2", :Symbol=>:three, :Fixnum=>1}

Is there a neater (one-line?) way I missed?

Ashley