add touch method to model

lib/Model.php

@@ -1270,6 +1270,33 @@ public function set_timestamps()
 			$this->created_at = $now;
 	}
 
+	/**
+	 * Touch a model, updates `updated_at` and any other column given as argument.
+	 *
+	 * Please note that no validation is performed and only the after_touch, after_commit and after_rollback callbacks are executed.
+	 *
+	 * @param string|array $keys...
+	 * @return bool True if update succeeds
+	 * @throws ActiveRecord\ActiveRecordException if object is a new record
+	 */
+	public function touch($keys = array() /*[, $key...] */)
+	{
+		if($this->is_new_record())
+			throw new ActiveRecordException('Cannot touch on a new record object');
+
+		if(!is_array($keys))
+			$keys = func_get_args();
+
+		if(!in_array('updated_at', $keys))
+			$keys[] = 'updated_at';
+
+		$now = date('Y-m-d H:i:s');
+		$attributes = array_fill_keys($keys, $now);
+
+		$this->set_attributes($attributes);
+		return $this->update(false);
+	}
+
 	/**
 	 * Mass update the model with attribute data and saves to the database.
 	 *

test/ActiveRecordWriteTest.php

@@ -441,4 +441,46 @@ public function test_update_our_datetime()
 		$this->assert_true($our_datetime === $author->some_date);
 	}
 
+	public function test_touch()
+	{
+		$author = Author::create(array('name' => 'MC Hammer'));
+		$updated_at = $author->updated_at = new DateTime('yesterday');
+		$author->save();
+		$author->touch();
+		$this->assertGreaterThan($updated_at, $author->updated_at);
+	}
+
+	/**
+	 * @expectedException ActiveRecord\ActiveRecordException
+	 * @expectedExceptionMessage Cannot touch on a new record object
+	 */
+	public function test_touch_on_new_record()
+	{
+		$author = new Author(array('name' => 'MC Hammer'));
+		$author->touch();
+	}
+
+	public function test_touch_with_additional_keys()
+	{
+		$author = Author::create(array('name' => 'MC Hammer'));
+		$updated_at = $author->updated_at = new DateTime('yesterday');
+		$some_date = $author->some_date = new DateTime('yesterday');
+		$author->save();
+		$author->touch(array('some_date'));
+		$this->assertGreaterThan($updated_at, $author->updated_at);
+		$this->assertGreaterThan($some_date, $author->some_date);
+	}
+
+	public function test_touch_with_scalar()
+	{
+		$author = Author::create(array('name' => 'MC Hammer'));
+		$updated_at = $author->updated_at = new DateTime('yesterday');
+		$some_date = $author->some_date = new DateTime('yesterday');
+		$author->save();
+		$author->touch('some_date');
+		$this->assertGreaterThan($updated_at, $author->updated_at);
+		$this->assertGreaterThan($some_date, $author->some_date);
+	}
+
+
 }