1 files changed, 28 insertions, 1 deletions
diff --git a/activesupport/lib/active_support/core_ext/enumerable.rb b/activesupport/lib/active_support/core_ext/enumerable.rb
index 49e1b7bb90..8a097dcd90 100644
--- a/activesupport/lib/active_support/core_ext/enumerable.rb
+++ b/activesupport/lib/active_support/core_ext/enumerable.rb
@@ -6,4 +6,31 @@ module Enumerable #:nodoc:
     end
     match
   end
-end
-\ No newline at end of file
+
+  # Collect an enumerable into sets, grouped by the result of a block. Useful,
+  # for example, for grouping records by date.
+  #
+  # e.g. 
+  #
+  #   latest_transcripts.group_by(&:day).each do |day, transcripts| 
+  #     p "#{day} -> #{transcripts.map(&:class) * ', '}"
+  #   end
+  #   "2006-03-01 -> Transcript"
+  #   "2006-02-28 -> Transcript"
+  #   "2006-02-27 -> Transcript, Transcript"
+  #   "2006-02-26 -> Transcript, Transcript"
+  #   "2006-02-25 -> Transcript"
+  #   "2006-02-24 -> Transcript, Transcript"
+  #   "2006-02-23 -> Transcript"
+  def group_by
+    inject([]) do |groups, element|
+      value = yield(element)
+      if (last_group = groups.last) && last_group.first == value
+        last_group.last << element
+      else
+        groups << [value, [element]]
+      end
+      groups
+    end
+  end
+end