1 files changed, 49 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/associations/association_proxy.rb b/activerecord/lib/active_record/associations/association_proxy.rb
new file mode 100644
index 0000000000..dcba207e20
--- /dev/null
+++ b/activerecord/lib/active_record/associations/association_proxy.rb
@@ -0,0 +1,49 @@
+module ActiveRecord
+  module Associations
+    class AssociationProxy #:nodoc:
+      alias_method :proxy_respond_to?, :respond_to?
+      instance_methods.each { |m| undef_method m unless m =~ /(^__|^nil\?|^proxy_respond_to\?|^send)/ }
+
+      def initialize(owner, association_name, association_class_name, association_class_primary_key_name, options)
+        @owner = owner
+        @options = options
+        @association_name = association_name
+        @association_class = eval(association_class_name)
+        @association_class_primary_key_name = association_class_primary_key_name
+
+        reset
+      end
+      
+      def method_missing(symbol, *args, &block)
+        load_target
+        @target.send(symbol, *args, &block)
+      end
+
+      def respond_to?(symbol, include_priv = false)
+        load_target
+        proxy_respond_to?(symbol, include_priv) || @target.respond_to?(symbol, include_priv)
+      end
+
+      def loaded?
+        @loaded
+      end
+
+      private
+        def load_target
+          unless @owner.new_record?
+            begin
+              @target = find_target if not loaded?
+            rescue ActiveRecord::RecordNotFound
+              reset
+            end
+          end
+          @loaded = true
+          @target
+        end
+
+        def raise_on_type_mismatch(record)
+          raise ActiveRecord::AssociationTypeMismatch, "#{@association_class} expected, got #{record.class}" unless record.is_a?(@association_class)
+        end
+    end
+  end
+end