1 files changed, 17 insertions, 4 deletions
diff --git a/guides/source/active_record_validations.md b/guides/source/active_record_validations.md
index 582bb240dd..8c832bafff 100644
--- a/guides/source/active_record_validations.md
+++ b/guides/source/active_record_validations.md
@@ -1,3 +1,5 @@
+**DO NOT READ THIS FILE IN GITHUB, GUIDES ARE PUBLISHED IN http://guides.rubyonrails.org.**
+
 Active Record Validations
 =========================
 
@@ -361,6 +363,8 @@ class Product < ActiveRecord::Base
 end
 ```
 
+Alternatively, you can require that the specified attribute does _not_ match the regular expression by using the `:without` option.
+
 The default error message is _"is invalid"_.
 
 ### `inclusion`
@@ -425,7 +429,7 @@ class Essay < ActiveRecord::Base
   validates :content, length: {
     minimum: 300,
     maximum: 400,
-    tokenizer: lambda { |str| str.scan(/\w+/) },
+    tokenizer: lambda { |str| str.split(/\s+/) },
     too_short: "must have at least %{count} words",
     too_long: "must have at most %{count} words"
   }
@@ -485,6 +489,8 @@ constraints to acceptable values:
 * `:even` - Specifies the value must be an even number if set to true. The
   default error message for this option is _"must be even"_.
 
+NOTE: By default, `numericality` doesn't allow `nil` values. You can use `allow_nil: true` option to permit it.
+
 The default error message is _"is not a number"_.
 
 ### `presence`
@@ -524,9 +530,16 @@ If you validate the presence of an object associated via a `has_one` or
 `marked_for_destruction?`.
 
 Since `false.blank?` is true, if you want to validate the presence of a boolean
-field you should use `validates :field_name, inclusion: { in: [true, false] }`.
+field you should use one of the following validations:
+
+```ruby
+validates :boolean_field_name, presence: true
+validates :boolean_field_name, inclusion: { in: [true, false] }
+validates :boolean_field_name, exclusion: { in: [nil] }
+```
 
-The default error message is _"can't be blank"_.
+By using one of these validations, you will ensure the value will NOT be `nil`
+which would result in a `NULL` value in most cases.
 
 ### `absence`
 
@@ -698,7 +711,7 @@ we don't want names and surnames to begin with lower case.
 ```ruby
 class Person < ActiveRecord::Base
   validates_each :name, :surname do |record, attr, value|
-    record.errors.add(attr, 'must start with upper case') if value =~ /\A[a-z]/
+    record.errors.add(attr, 'must start with upper case') if value =~ /\A[[:lower:]]/
   end
 end
 ```