Require `belongs_to` by default.

Deprecate `required` option in favor of `optional` for belongs_to.

2 files changed, 7 insertions, 0 deletions

diff --git a/guides/source/association_basics.md b/guides/source/association_basics.md
index cd715aba1f..0079049d44 100644
--- a/guides/source/association_basics.md
+++ b/guides/source/association_basics.md
@@ -833,6 +833,7 @@ The `belongs_to` association supports these options:
 * `:polymorphic`
 * `:touch`
 * `:validate`
+* `:optional`
 
 ##### `:autosave`
 
@@ -956,6 +957,10 @@ end
 
 If you set the `:validate` option to `true`, then associated objects will be validated whenever you save this object. By default, this is `false`: associated objects will not be validated when this object is saved.
 
+##### `:optional`
+
+If you set the `:optional` option to `true`, then associated object will be validated for presence. By default, this is `false`: associated objects will be validated for presence.
+
 #### Scopes for `belongs_to`
 
 There may be times when you wish to customize the query used by `belongs_to`. Such customizations can be achieved via a scope block. For example:
diff --git a/guides/source/configuring.md b/guides/source/configuring.md
index ab1cc9306f..4fc1301e06 100644
--- a/guides/source/configuring.md
+++ b/guides/source/configuring.md
@@ -300,6 +300,8 @@ All these configuration options are delegated to the `I18n` library.
   `config/environments/production.rb` which is generated by Rails. The
   default value is true if this configuration is not set.
 
+* `config.active_record.belongs_to_required_by_default` is a boolean value and controls whether `belongs_to` association is required by default.
+
 The MySQL adapter adds one additional configuration option:
 
 * `ActiveRecord::ConnectionAdapters::MysqlAdapter.emulate_booleans` controls whether Active Record will consider all `tinyint(1)` columns in a MySQL database to be booleans and is true by default.