documents the backported Range#cover?, and related stuff

1 files changed, 5 insertions, 3 deletions

diff --git a/activemodel/lib/active_model/validations/inclusion.rb b/activemodel/lib/active_model/validations/inclusion.rb
index b0903a6a2c..3ee2a3ccd1 100644
--- a/activemodel/lib/active_model/validations/inclusion.rb
+++ b/activemodel/lib/active_model/validations/inclusion.rb
@@ -14,9 +14,9 @@ module ActiveModel
         record.errors.add(attribute, :inclusion, options.except(:in).merge!(:value => value)) unless options[:in].send(include?, value)
       end
 
-      # On Ruby 1.9 Range#include? checks all possible values in the range for equality,
-      # so it may be slow for large ranges. The new Range#cover? uses the previous logic
-      # of comparing a value with the range endpoints.
+      # In Ruby 1.9 <tt>Range#include?</tt> on non-numeric ranges checks all possible values in the
+      # range for equality, so it may be slow for large ranges. The new <tt>Range#cover?</tt>
+      # uses the previous logic of comparing a value with the range endpoints.
       def include?
         options[:in].is_a?(Range) ? :cover? : :include?
       end
@@ -33,6 +33,8 @@ module ActiveModel
       #
       # Configuration options:
       # * <tt>:in</tt> - An enumerable object of available items.
+      #   If the enumerable is a range the test is performed with <tt>Range#cover?</tt>
+      #   (backported in Active Support for 1.8), otherwise with <tt>include?</tt>.
       # * <tt>:message</tt> - Specifies a custom error message (default is: "is not included in the list").
       # * <tt>:allow_nil</tt> - If set to true, skips this validation if the attribute is +nil+ (default is +false+).
       # * <tt>:allow_blank</tt> - If set to true, skips this validation if the attribute is blank (default is +false+).