Ruby Memoize

ruby-memoize.md

Memoize memoizes function return values based on class name, method name, and arguments. This means that this only works for functions that use state / have side effects.

module Memoize
  def memoize(definition)	
    self.send(:alias_method, "__original_#{definition}", definition)

    define_method definition, Proc.new { |*args|
      @__memo ||= {}

      key = "#{self.class.name}##{definition}/#{args.hash}"
      return @__memo[key] if @__memo.key?(key)

      @__memo[key] = send("__original_#{definition}", *args)
    }
  end
end

Usage

class A
  class B
    extend Memoize
  
    def heavy_calculation(a, b)
      p "calling the original"
      a * b
    end
    
    memoize :heavy_calculation
  end	
end

b = A::B.new

p b.heavy_calculation(4, 20)
# "calling the original"
# 80
p b.heavy_calculation(4, 20)
# 80
p b.heavy_calculation(2, 20)
# "calling the original"
# 40