Add Touch method to ActiveRelation

activerecord/lib/active_record/relation.rb

@@ -519,7 +519,33 @@ def to_sql
                   end
     end
 
-    # Returns a hash of where conditions.
+    # Touches multiple records.
+    #
+    # === Examples
+    #
+    #   # Touch all records
+    #   Person.all.touch
+    #   # => "UPDATE \"persons\" SET \"updated_at\" = '2063-04-04 22:55:23.132670'"
+    #
+    #   # Touch multiple records with a custom attribute
+    #   Person.all.touch(:created_at)
+    #   # => "UPDATE \"persons\" SET \"updated_at\" = '2012-11-27 23:12:25.745411', \"created_at\" = '2012-11-27 23:12:25.745411'"
+    #
+    #   # Touch records with scope
+    #   Person.where(:name => 'David').touch
+    #   # => "UPDATE \"persons\" SET \"updated_at\" = '2012-11-27 23:12:30.087110' WHERE \"persons\".\"name\" = 'David'"
+    def touch(name = nil)
+      attributes = [:updated_at]
+      attributes << name if name
+      now = klass.default_timezone == :utc ? Time.now.utc : Time.now
+      value_hash = attributes.inject({}) do |values, column|
+        values[column] = now
+        values
+      end
+      update_all(value_hash)
+    end
+
+    # Returns a hash of where conditions
     #
     #   User.where(name: 'Oscar').where_values_hash
     #   # => {name: "Oscar"}

activerecord/test/cases/relations_test.rb

@@ -1391,6 +1391,24 @@ def test_presence
     assert topics.loaded?
   end
 
+  def test_touching_multiple_record_updates_their_timestamps
+    Developer.all.touch
+    assert Developer.first.updated_at >= 1.second.ago, "First Developer was not updated"
+    assert Developer.last.updated_at >= 1.second.ago,  "Last Developer was not updated"
+  end
+
+  def test_touching_multiple_record_with_custom_timestamp
+    Developer.all.touch(:created_at)
+    assert Developer.first.created_at >= 1.second.ago
+    assert Developer.last.created_at >= 1.second.ago
+  end
+
+  def test_touching_records_from_a_scope
+    Developer.where(:name => 'David').touch
+    assert Developer.first.updated_at >= 1.second.ago, "First Developer was not updated"
+    assert Developer.last.updated_at <= 1.second.ago,  "Last Developer was updated"
+  end
+
   test "find_by with hash conditions returns the first matching record" do
     assert_equal posts(:eager_other), Post.order(:id).find_by(author_id: 2)
   end

activerecord/test/fixtures/developers.yml

@@ -2,20 +2,32 @@ david:
   id: 1
   name: David
   salary: 80000
+  created_at: <%= 10.minutes.ago.to_s(:db) %>
+  updated_at: <%= 5.minutes.ago.to_s(:db) %>
+  updated_on: <%= 5.minutes.ago.to_s(:db) %>
 
 jamis:
   id: 2
   name: Jamis
   salary: 150000
+  created_at: <%= 15.minutes.ago.to_s(:db) %>
+  updated_at: <%= 12.minutes.ago.to_s(:db) %>
+  updated_on: <%= 12.minutes.ago.to_s(:db) %>
 
 <% (3..10).each do |digit| %>
 dev_<%= digit %>:
   id: <%= digit %>
   name: fixture_<%= digit %>
   salary: 100000
+  created_at: <%= (digit+5).minutes.ago.to_s(:db) %>
+  updated_at: <%= digit.minutes.ago.to_s(:db) %>
+  updated_on: <%= digit.minutes.ago.to_s(:db) %>
 <% end %>
 
 poor_jamis:
   id: 11
   name: Jamis
-  salary: 9000
+  salary: 9000
+  created_at: <%= 20.minutes.ago.to_s(:db) %>
+  updated_at: <%= 16.minutes.ago.to_s(:db) %>
+  updated_on: <%= 16.minutes.ago.to_s(:db) %>