Cacheable attributes

cacheable_attr.rb

module CacheableAttr
  
  def cacheable_attr(*attributes)
    opts = { ttl: 60 }
    opts = opts.merge(attributes.pop) if attributes.last.is_a?(Hash)
    
    attributes.each do |attribute|
      define_method attribute do
        if !instance_variable_defined?("@#{attribute}_updated_at") || (opts[:ttl] != nil && Time.now >= instance_variable_get("@#{attribute}_updated_at") + opts[:ttl])
          value = send("#{attribute}_uncached")
          instance_variable_set("@#{attribute}", value)
          instance_variable_set("@#{attribute}_updated_at", Time.now)
        end
        
        instance_variable_get("@#{attribute}")
      end
    end
  end
  
end

# ================================================================================= #
# = EXAMPLE ======================================================================= #
# ================================================================================= #

class NumberGenerator
  extend CacheableAttr
  
  cacheable_attr :num1, ttl: 3
  cacheable_attr :num2, ttl: 0
  cacheable_attr :num3, ttl: nil
  
  def num1_uncached
    rand(100)
  end
  
  def num2_uncached
    rand(100)
  end
  
  def num3_uncached
    rand(100)
  end
end

num_gen = NumberGenerator.new


puts "The first number will change every 3 seconds"
puts "The second number will change every single call"
puts "The third number will never change"
puts ""

loop do
  puts "[#{Time.now}] #{'%02d' % num_gen.num1} - #{'%02d' % num_gen.num2} - #{'%02d' % num_gen.num3}"
  sleep 0.5
end