Memoize in Ruby

memoize.rb

# Memoize with extend

module Memoize
  def memoize(method)
    unmemoized_name = :"__unmemoized_#{method}"

    alias_method unmemoized_name, method

    define_method method do
      @__memoized_results ||= {}

      if @__memoized_results.include? method
        p "Call from memoize"
        @__memoized_results[method]
      else
        p "First time call"
        @__memoized_results[method] = send(unmemoized_name)
      end
    end
  end
end

class A
  extend Memoize

  def t1
    10
  end
  memoize :t1
end

a = A.new

p a.t1 # First time call
p a.t1 # Call from memoize
p a.t1 # Call from memoize
p a.t1 # Call from memoize


# Memoize with prepend

module Memoize
  def memoize(method)
    memoizer = Module.new do
      define_method method do
        @__memoized_results ||= {}

      if @__memoized_results.include? method
        p "Call from memoize"
        @__memoized_results[method]
      else
        p "First time call"
        @__memoized_results[method] = super()
      end
      end
    end

    prepend memoizer
  end
end

class B
  extend Memoize

  def t1
    10
  end
  memoize :t1
end

p B.ancestors

b = B.new

p b.t1 # First time call
p b.t1 # Call from memoize
p b.t1 # Call from memoize
p b.t1 # Call from memoize