Add docs and changelog entry for 73aab036 [ci skip]

activerecord/CHANGELOG.md

@@ -11,6 +11,11 @@
 
     *Ryuta Kamizono*
 
+*   Allow proc defaults to be passed to the attributes API. See documentation
+    for examples.
+
+    *Sean Griffin, Kir Shatrov*
+
 *   SQLite: `:collation` support for string and text columns.
 
     Example:

activerecord/lib/active_record/attributes.rb

@@ -82,6 +82,14 @@ module ClassMethods
       #
       #   StoreListing.new.my_string # => "new default"
       #
+      #   class Product < ActiveRecord::Base
+      #     attribute :my_default_proc, :datetime, default: -> { Time.now }
+      #   end
+      #
+      #   Product.new.my_default_proc # => 2015-05-30 11:04:48 -0600
+      #   sleep 1
+      #   Product.new.my_default_proc # => 2015-05-30 11:04:49 -0600
+      #
       # Attributes do not need to be backed by a database column.
       #
       #   class MyModel < ActiveRecord::Base
@@ -204,7 +212,8 @@ def attribute(name, cast_type, **options)
       #
       # +default+ The default value to use when no value is provided. If this option
       # is not passed, the previous default value (if any) will be used.
-      # Otherwise, the default will be +nil+.
+      # Otherwise, the default will be +nil+. A proc can also be passed, and
+      # will be called once each time a new value is needed.
       #
       # +user_provided_default+ Whether the default value should be cast using
       # +cast+ or +deserialize+.