Playing with selecting and sorting of Hash

hash.rb

class Hash

  def select_and_sort_by(whitelist)
    whitelist.inject({}) do |h,k| 
      k = k.to_sym if k.is_a? String
      h[k] = self[k] if self.has_key? k
      h
    end
  end
  
end

# collection.select_and_sort_by({:key1, :key3})