Make sure raise error if you try to overwrite field name that is already defined in Object

lib/active_hash/base.rb

@@ -280,7 +280,7 @@ def add_default_value field_name, default_value
       end
 
       def define_getter_method(field, default_value)
-        unless instance_methods.include?(field.to_sym)
+        unless instance_methods(false).include?(field.to_sym)
           define_method(field) do
             attributes[field].nil? ? default_value : attributes[field]
           end
@@ -291,7 +291,7 @@ def define_getter_method(field, default_value)
 
       def define_setter_method(field)
         method_name = :"#{field}="
-        unless instance_methods.include?(method_name)
+        unless instance_methods(false).include?(method_name)
           define_method(method_name) do |new_val|
             @attributes[field] = new_val
           end
@@ -302,7 +302,7 @@ def define_setter_method(field)
 
       def define_interrogator_method(field)
         method_name = :"#{field}?"
-        unless instance_methods.include?(method_name)
+        unless instance_methods(false).include?(method_name)
           define_method(method_name) do
             send(field).present?
           end
@@ -313,7 +313,7 @@ def define_interrogator_method(field)
 
       def define_custom_find_method(field_name)
         method_name = :"find_by_#{field_name}"
-        unless singleton_methods.include?(method_name)
+        unless singleton_methods(false).include?(method_name)
           the_meta_class.instance_eval do
             define_method(method_name) do |*args|
               args.extract_options!
@@ -328,9 +328,9 @@ def define_custom_find_method(field_name)
 
       def define_custom_find_all_method(field_name)
         method_name = :"find_all_by_#{field_name}"
-        unless singleton_methods.include?(method_name)
+        unless singleton_methods(false).include?(method_name)
           the_meta_class.instance_eval do
-            unless singleton_methods.include?(method_name)
+            unless singleton_methods(false).include?(method_name)
               define_method(method_name) do |*args|
                 args.extract_options!
                 identifier = args[0]

spec/active_hash/base_spec.rb

@@ -1172,41 +1172,57 @@ class Region < ActiveHash::Base
       end
     end
 
-    it "doesn't override methods already defined" do
-      Country.class_eval do
-        class << self
-          def find_by_name(name)
-            "find_by_name defined manually"
+    context "when Country already defined name methods" do
+      before do
+        Country.class_eval do
+          class << self
+            def find_by_name(name)
+              "find_by_name defined manually"
+            end
+
+            def find_all_by_name(name)
+              "find_all_by_name defined manually"
+            end
           end
 
-          def find_all_by_name(name)
-            "find_all_by_name defined manually"
+          def name
+            "name defined manually"
           end
-        end
-
-        def name
-          "name defined manually"
-        end
 
-        def name?
-          "name? defined manually"
+          def name?
+            "name? defined manually"
+          end
         end
       end
 
-      Country.find_by_name("foo").should == "find_by_name defined manually"
-      Country.find_all_by_name("foo").should == "find_all_by_name defined manually"
-      Country.new.name.should == "name defined manually"
-      Country.new.name?.should == "name? defined manually"
+      it "doesn't override methods already defined" do
+        Country.find_by_name("foo").should == "find_by_name defined manually"
+        Country.find_all_by_name("foo").should == "find_all_by_name defined manually"
+        Country.new.name.should == "name defined manually"
+        Country.new.name?.should == "name? defined manually"
 
-      Country.data = [
-        {:name => "foo"}
-      ]
+        Country.data = [
+          {:name => "foo"}
+        ]
+
+        Country.all
+        Country.find_by_name("foo").should == "find_by_name defined manually"
+        Country.find_all_by_name("foo").should == "find_all_by_name defined manually"
+        Country.new.name.should == "name defined manually"
+        Country.new.name?.should == "name? defined manually"
+      end
 
-      Country.all
-      Country.find_by_name("foo").should == "find_by_name defined manually"
-      Country.find_all_by_name("foo").should == "find_all_by_name defined manually"
-      Country.new.name.should == "name defined manually"
-      Country.new.name?.should == "name? defined manually"
+      it "allow override methods already defined in super class" do
+        class Japan < Country
+          field :name
+          add name: "bar"
+        end
+        Japan.first.name.should == "bar"
+        Japan.find_by_name("bar").should be_a(Japan)
+        Japan.find_all_by_name("bar").should be_a(Array) 
+        Japan.first.name.should == "bar"
+        Japan.first.name?.should be_truthy
+      end
     end
   end