Add memoization to methods when they are added

lib/adamantium.rb

@@ -47,10 +47,7 @@ def self.included(descendant)
     descendant.class_eval do
       include Memoizable
       extend ModuleMethods
-      if instance_of?(Class)
-        extend ClassMethods
-        memoize(:hash, :inspect, :to_s)
-      end
+      extend ClassMethods if instance_of?(Class)
     end
   end
   private_class_method :included

lib/adamantium/module_methods.rb

@@ -4,6 +4,8 @@ module Adamantium
 
   # Methods mixed in to adamantium modules
   module ModuleMethods
+    MEMOIZE_METHODS = [:hash, :inspect, :to_s].freeze
+    RECURSION_GUARD = IceNine::RecursionGuard::ObjectSet.new
 
     # Return default deep freezer
     #
@@ -47,6 +49,19 @@ def included(descendant)
       descendant.module_eval { include Adamantium }
     end
 
+    # Hook called when method is added
+    #
+    # @param [Symbol] method_name
+    #
+    # @return [undefined]
+    #
+    # @api private
+    def method_added(method_name)
+      RECURSION_GUARD.guard(self) do
+        memoize(method_name) if MEMOIZE_METHODS.include?(method_name)
+      end
+    end
+
     # Memoize the named method
     #
     # @param [Symbol] method_name

spec/unit/adamantium/hash_spec.rb

@@ -6,8 +6,18 @@
 describe Adamantium, '#hash' do
   subject { object.hash }
 
-  let(:object)          { described_class.new     }
-  let(:described_class) { AdamantiumSpecs::Object }
+  let(:object) { described_class.new }
+
+  let(:described_class) do
+    Class.new(AdamantiumSpecs::Object) do
+      FIXNUM_MAX = 2**(0.size * 8 - 2) - 1
+      FIXNUM_MIN = -2**(0.size * 8 - 2)
+
+      def hash
+        Random.rand(FIXNUM_MIN..FIXNUM_MAX)
+      end
+    end
+  end
 
   it_behaves_like 'a hash method'
 end

spec/unit/adamantium/inspect_spec.rb

@@ -6,8 +6,15 @@
 describe Adamantium, '#inspect' do
   subject { object.inspect }
 
-  let(:object)          { described_class.new     }
-  let(:described_class) { AdamantiumSpecs::Object }
+  let(:object) { described_class.new }
+
+  let(:described_class) do
+    Class.new(AdamantiumSpecs::Object) do
+      def inspect
+        rand.to_s
+      end
+    end
+  end
 
   it_behaves_like 'an idempotent method'
 end

spec/unit/adamantium/to_s_spec.rb

@@ -6,8 +6,15 @@
 describe Adamantium, '#to_s' do
   subject { object.to_s }
 
-  let(:object)          { described_class.new     }
-  let(:described_class) { AdamantiumSpecs::Object }
+  let(:object) { described_class.new }
+
+  let(:described_class) do
+    Class.new(AdamantiumSpecs::Object) do
+      def to_s
+        rand.to_s
+      end
+    end
+  end
 
   it_behaves_like 'an idempotent method'
 end