I feel like there is a whole blog post in here.

memoize_and_reset.rb

 class Test
   def initialize
     puts "I've been created"
   end
 end


 module Foo
   def self.check
     tester
   end
   def self.tester
     @tester ||= Test.new
   end
   def self.reset
     @tester = nil # Will 'empty' the ivar, but not actually 'remove' it from the object.
   end
 end

Foo.instance_variables #=> []
Foo.check
Foo.instance_variables #=> [:@tester]
Foo.reset
Foo.instance_variables #=> [:@tester]