ruby number to human-readable string conversion

Question

I need to have a list with id's for each list item being #one, #two etc. Is this the most efficient way or am I missing an in built ruby function here?

-num_array = ["one", "two", "three", "four", "five", "six", "seven"]
-navigation[:primary_level].each_with_index do |primary_item, idx|
   %li{ :id => "#{num_array[idx]}"}

Answer 1

I'm sure this goes well beyond what you need, but there's code to do that at Rosetta Code

Answer 2

The humanize gem converts digits into words.