Make Memoize more object shapes friendly

lib/rodbot/memoize.rb

@@ -45,6 +45,19 @@ module Rodbot
   #     e.either(5)               # => 5          (recalculated, memoized anew)
   #   end
   module Memoize
+
+    # Set up the memoize cache in the initializer in order to keep the number of
+    # object shapes low. There's still a fallback in the +memoize+ method for
+    # use cases where no object is instantiated.
+    #
+    # @see https://island94.org/2023/10/writing-object-shape-friendly-code-in-ruby
+    module Initializer
+      def initialize(...)
+        @_memoize_cache = {}
+        super
+      end
+    end
+
     module ClassMethods
       def memoize(method)
         unmemoized_method = :"_unmemoized_#{method}"
@@ -54,7 +67,7 @@ def memoize(method)
             send(unmemoized_method, *args, **kargs, &block)
           else
             id = method.hash ^ args.hash ^ kargs.hash
-            @_memoize_cache ||= {}
+            @_memoize_cache ||= {}   # fallback memoize cache setup
             if !Rodbot::Memoize.revisit? && @_memoize_cache.has_key?(id)
               @_memoize_cache[id]
             else
@@ -86,6 +99,7 @@ class << self
       end
 
       def included(base)
+        base.prepend(Initializer)
         base.extend(ClassMethods)
       end
     end

spec/lib/rodbot/concerns/memoize_spec.rb

@@ -1,4 +1,4 @@
-require_relative '../../../spec_helper'
+#require_relative '../../../spec_helper'
 
 class Either
   include Rodbot::Memoize