An example of memoization using Ruby 2's module prepend.

memoize.rb

module Memoize
  def calc(n)
    @@memo ||= {}
    @@memo[n] ||= super
  end
end

class Fibonacci
  prepend Memoize

  def calc(n)
    return n if n < 2
    return calc(n - 1) + calc(n - 2)
  end
end

puts Fibonacci.new.calc(36)