1 files changed, 42 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/associations/builder/singular_association.rb b/activerecord/lib/active_record/associations/builder/singular_association.rb
new file mode 100644
index 0000000000..0a02ef4cc1
--- /dev/null
+++ b/activerecord/lib/active_record/associations/builder/singular_association.rb
@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+
+# This class is inherited by the has_one and belongs_to association classes
+
+module ActiveRecord::Associations::Builder # :nodoc:
+  class SingularAssociation < Association #:nodoc:
+    def self.valid_options(options)
+      super + [:foreign_type, :dependent, :primary_key, :inverse_of, :required]
+    end
+
+    def self.define_accessors(model, reflection)
+      super
+      mixin = model.generated_association_methods
+      name = reflection.name
+
+      define_constructors(mixin, name) if reflection.constructable?
+
+      mixin.class_eval <<-CODE, __FILE__, __LINE__ + 1
+        def reload_#{name}
+          association(:#{name}).force_reload_reader
+        end
+      CODE
+    end
+
+    # Defines the (build|create)_association methods for belongs_to or has_one association
+    def self.define_constructors(mixin, name)
+      mixin.class_eval <<-CODE, __FILE__, __LINE__ + 1
+        def build_#{name}(*args, &block)
+          association(:#{name}).build(*args, &block)
+        end
+
+        def create_#{name}(*args, &block)
+          association(:#{name}).create(*args, &block)
+        end
+
+        def create_#{name}!(*args, &block)
+          association(:#{name}).create!(*args, &block)
+        end
+      CODE
+    end
+  end
+end