Cleanest way to create a Hash from an Array

Question

I seem to run into this very often. I need to build a Hash from an array using an attribute of each object in the array as the key.

Lets say I need a hash of example us

Answer 1

a shortest one?

# 'Region' is a sample class here
# you can put 'self.to_hash' method into any class you like 

class Region < ActiveRecord::Base
  def self.to_hash
    Hash[*all.map{ |x| [x.id, x] }.flatten]
  end
end