cakephp: question about caching cakephp

i use var $cacheAction = '1 hour'; cakephp create file xxx_view_1245.php in cache/views/ , it cached. but if i use

var $cacheActi开发者_运维百科on = array(
          'view/' => '1 hour'
 );

cakephp dont cache, i dont know why , please help me

if I use var

$cacheAction = array(
          'view' => '1 hour',
          'index'=>'1 hour'
 );

then it'll cache. WTF documentation: http://book.cakephp.org/view/1380/Caching-in-the-Controller.