1 files changed, 61 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/associations/builder/has_one.rb b/activerecord/lib/active_record/associations/builder/has_one.rb
new file mode 100644
index 0000000000..07ba5d088e
--- /dev/null
+++ b/activerecord/lib/active_record/associations/builder/has_one.rb
@@ -0,0 +1,61 @@
+module ActiveRecord::Associations::Builder
+  class HasOne < SingularAssociation #:nodoc:
+    self.macro = :has_one
+
+    self.valid_options += [:order, :as]
+
+    class_attribute :through_options
+    self.through_options = [:through, :source, :source_type]
+
+    def constructable?
+      !options[:through]
+    end
+
+    def build
+      reflection = super
+      configure_dependency unless options[:through]
+      reflection
+    end
+
+    private
+
+      def validate_options
+        valid_options = self.class.valid_options
+        valid_options += self.class.through_options if options[:through]
+        options.assert_valid_keys(valid_options)
+      end
+
+      def configure_dependency
+        if options[:dependent]
+          unless [:destroy, :delete, :nullify, :restrict].include?(options[:dependent])
+            raise ArgumentError, "The :dependent option expects either :destroy, :delete, " \
+                                 ":nullify or :restrict (#{options[:dependent].inspect})"
+          end
+
+          send("define_#{options[:dependent]}_dependency_method")
+          model.before_destroy dependency_method_name
+        end
+      end
+
+      def dependency_method_name
+        "has_one_dependent_#{options[:dependent]}_for_#{name}"
+      end
+
+      def define_destroy_dependency_method
+        model.send(:class_eval, <<-eoruby, __FILE__, __LINE__ + 1)
+          def #{dependency_method_name}
+            association(#{name.to_sym.inspect}).delete
+          end
+        eoruby
+      end
+      alias :define_delete_dependency_method :define_destroy_dependency_method
+      alias :define_nullify_dependency_method :define_destroy_dependency_method
+
+      def define_restrict_dependency_method
+        name = self.name
+        model.redefine_method(dependency_method_name) do
+          raise ActiveRecord::DeleteRestrictionError.new(name) unless send(name).nil?
+        end
+      end
+  end
+end