cachemire.rb

module Cachemire
  extend ActiveSupport::Concern

  included do
    class_attribute :cache_store
  end

  module ClassMethods

    private

    def cache_result(&block)
      cache_store.fetch("#{object_id}_#{caller_locations(1,1)[0].label}") do
        block.call
      end
    end
  end


  private

  def cache_result(&block)
    cache_store.fetch("#{object_id}_#{caller_locations(1,1)[0].label}") do
      block.call
    end
  end
end

world.rb

class World
  include Cachemire

  self.cache_store = ActiveSupport::Cache::MemoryStore.new

  def self.get_population_count
    cache_result do
      # Intense stuff...
    end
  end

  def get_population_count
    cache_result do
      # Intense stuff...
    end
  end
end