1 files changed, 55 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/associations/singular_association.rb b/activerecord/lib/active_record/associations/singular_association.rb
new file mode 100644
index 0000000000..4edbe216be
--- /dev/null
+++ b/activerecord/lib/active_record/associations/singular_association.rb
@@ -0,0 +1,55 @@
+module ActiveRecord
+  module Associations
+    class SingularAssociation < Association #:nodoc:
+      # Implements the reader method, e.g. foo.bar for Foo.has_one :bar
+      def reader(force_reload = false)
+        if force_reload
+          klass.uncached { reload }
+        elsif !loaded? || stale_target?
+          reload
+        end
+
+        target
+      end
+
+      # Implements the writer method, e.g. foo.items= for Foo.has_many :items
+      def writer(record)
+        replace(record)
+      end
+
+      def create(attributes = {})
+        new_record(:create, attributes)
+      end
+
+      def create!(attributes = {})
+        build(attributes).tap { |record| record.save! }
+      end
+
+      def build(attributes = {})
+        new_record(:build, attributes)
+      end
+
+      private
+
+        def find_target
+          scoped.first.tap { |record| set_inverse_instance(record) }
+        end
+
+        # Implemented by subclasses
+        def replace(record)
+          raise NotImplementedError, "Subclasses must implement a replace(record) method"
+        end
+
+        def set_new_record(record)
+          replace(record)
+        end
+
+        def new_record(method, attributes)
+          attributes = scoped.scope_for_create.merge(attributes || {})
+          record = reflection.send("#{method}_association", attributes)
+          set_new_record(record)
+          record
+        end
+    end
+  end
+end