Document validates_presences_of behavior with booleans: you probably want...

Document validates_presences_of behavior with booleans: you probably want validates_inclusion_of :attr, :in => [true, false]. Closes #2253.

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@4980 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activerecord/CHANGELOG

 *SVN*
 
+* Document validates_presences_of behavior with booleans: you probably want validates_inclusion_of :attr, :in => [true, false].  #2253 [Bob Silva]
+
 * Optimistic locking: gracefully handle nil versions, treat as zero.  #5908 [Tom Ward]
 
 * validates_confirmation_of only kicks in when the attribute, rather than its confirmation, is present.  #785 [z@wzph.com]

activerecord/lib/active_record/validations.rb

@@ -375,6 +375,10 @@ def validates_acceptance_of(*attr_names)
       #
       # The first_name attribute must be in the object and it cannot be blank.
       #      
+      # If you want to validate the presence of a boolean field (where the real values are true and false),
+      # you will want to use validates_inclusion_of :field_name, :in => [true, false]
+      # This is due to the way Object#blank? handles boolean values. false.blank? # => true
+      #
       # Configuration options:
       # * <tt>message</tt> - A custom error message (default is: "can't be blank")
       # * <tt>on</tt> - Specifies when this validation is active (default is :save, other options :create, :update)