A class-wrapping memoization dingus

memo_me.rb

def MemoMe(superclass)
  # Ripped mostly out of
  #   https://github.com/ruby/ruby/blob/trunk/lib/delegate.rb
  klass = Class.new(superclass)
  methods = superclass.instance_methods
  methods -= [:to_s, :inspect, :=~, :!~, :===, :instance_variable_get, :instance_variable_set]
  klass.define_method(:initialize, lambda do |*args|
    @__memo_me_instance = superclass.new(*args)
  end)
  klass.module_eval do
    methods.each do |method|
      define_method(method, lambda do |*args, &block|
        target = self.instance_variable_get("@__memo_me_instance")#.__getobj__

        cache = target.instance_variable_get("@__memo_me_store") ||
          target.instance_variable_set("@__memo_me_store", {})
        cache[method] ||= {}

        if memo = cache[method][[args, block]]
          return memo
        else
          cache[method][[args, block]] = target.__send__(method, *args, &block)
        end
      end)
    end
  end
  klass.define_singleton_method :public_instance_methods do |all=true|
    super(all) - superclass.protected_instance_methods
  end
  klass.define_singleton_method :protected_instance_methods do |all=true|
    super(all) | superclass.protected_instance_methods
  end
  return klass
end

# Demo:

class Calculator
  def add(a, b)
    puts "Ugh adding two numbers is so expensive"
    a + b
  end
end

CachingCalculator = MemoMe(Calculator)

calculator = CachingCalculator.new

puts calculator.add(1, 1)
puts calculator.add(2, 2)

puts <<~TEXT
  No more printing! Just math!
  ---
TEXT

calculator.add(1, 1)
calculator.add(2, 2)