1 files changed, 18 insertions, 6 deletions
diff --git a/activerecord/lib/active_record/nested_attributes.rb b/activerecord/lib/active_record/nested_attributes.rb
index 01ecd79b8f..fa20bce3a9 100644
--- a/activerecord/lib/active_record/nested_attributes.rb
+++ b/activerecord/lib/active_record/nested_attributes.rb
@@ -1,4 +1,7 @@
+# frozen_string_literal: true
+
 require "active_support/core_ext/hash/except"
+require "active_support/core_ext/module/redefine_method"
 require "active_support/core_ext/object/try"
 require "active_support/core_ext/hash/indifferent_access"
 
@@ -10,8 +13,7 @@ module ActiveRecord
     extend ActiveSupport::Concern
 
     included do
-      class_attribute :nested_attributes_options, instance_writer: false
-      self.nested_attributes_options = {}
+      class_attribute :nested_attributes_options, instance_writer: false, default: {}
     end
 
     # = Active Record Nested Attributes
@@ -61,6 +63,18 @@ module ActiveRecord
     #   member.update params[:member]
     #   member.avatar.icon # => 'sad'
     #
+    # If you want to update the current avatar without providing the id, you must add <tt>:update_only</tt> option.
+    #
+    #   class Member < ActiveRecord::Base
+    #     has_one :avatar
+    #     accepts_nested_attributes_for :avatar, update_only: true
+    #   end
+    #
+    #   params = { member: { avatar_attributes: { icon: 'sad' } } }
+    #   member.update params[:member]
+    #   member.avatar.id # => 2
+    #   member.avatar.icon # => 'sad'
+    #
     # By default you will only be able to set and update attributes on the
     # associated model. If you want to destroy the associated model through the
     # attributes hash, you have to enable it first using the
@@ -354,9 +368,7 @@ module ActiveRecord
         # associations are just regular associations.
         def generate_association_writer(association_name, type)
           generated_association_methods.module_eval <<-eoruby, __FILE__, __LINE__ + 1
-            if method_defined?(:#{association_name}_attributes=)
-              remove_method(:#{association_name}_attributes=)
-            end
+            silence_redefinition_of_method :#{association_name}_attributes=
             def #{association_name}_attributes=(attributes)
               assign_nested_attributes_for_#{type}_association(:#{association_name}, attributes)
             end
@@ -458,7 +470,7 @@ module ActiveRecord
         end
 
         unless attributes_collection.is_a?(Hash) || attributes_collection.is_a?(Array)
-          raise ArgumentError, "Hash or Array expected, got #{attributes_collection.class.name} (#{attributes_collection.inspect})"
+          raise ArgumentError, "Hash or Array expected for attribute `#{association_name}`, got #{attributes_collection.class.name} (#{attributes_collection.inspect})"
         end
 
         check_record_limit!(options[:limit], attributes_collection)