Memoization Helper

memoize.rb

# Replaces repetitive memoization syntax:
# ```
# def foo
#   return @_foo if defined? @_foo
#   @_foo = 'bar'
# end
# ```
#
# Usage:
#
# ```
# require 'memoize'
#
# class Foo
#   def bar
#     memoize { 'baz' }
#   end
# end
# ```
def memoize(meth = nil)
  variable_name = "@_#{meth || caller_locations(1, 1)[0].label}".to_sym
  receiver = binding.receiver

  if receiver.instance_variable_defined?(variable_name)
    receiver.instance_variable_get(variable_name)
  else
    receiver.instance_variable_set(variable_name, yield)
  end
end

Nice one @stuartc - am definitely gonna use this.