DSL for querying nth_letter of string.

nth_letter.rb

def self.method_missing(method, *args)
  number_dictionary = {
    first: 1,
    second: 2,
    third: 3,
    fourth: 4,
    fifth: 5,
    sixth: 6,
    seventh: 7,
    eigth: 8,
    ninth: 9,
    tenth: 10
  }

  if method.to_s =~ /(.+)_letter/ && number = number_dictionary[$1.to_sym]
    args[0][number - 1]
  else
    super
  end
end

first_letter('hey')   # h     
second_letter('hey')  # e
third_letter('hey')   # y