Rails3使用jquery rjs，可能需要注意的地方。mark

这里假设你使用rails3, jquery rails.js

你想实现ajax loading效果，却发现rails的tag里只使用:remote => true
并没有rails2里使用的loading函数。
我看了rails.js，看到

The UJS drivers trigger six events on every AJAX call:

• ajax:before
• ajax:loading
• ajax:success
• ajax:failure
• ajax:complete
• ajax:after

但是怎么使用是个问题。
看了这个ticket，就知道并不是所有人了解：
https://rails.lighthouseapp.com/projects/8994/tickets/4486-new-ujs-helpers-do-not-have-a-way-to-render-a-loading-text-icon
his can easily be accomplished each driver has a custom callback that fires before the request is sent, here is an example using the jQuery driver.

  $('#new_resource').live('ajax:loading', function() {
     // code to display loading div
  });

refs:
https://rails.lighthouseapp.com/projects/8994/tickets/4486-new-ujs-helpers-do-not-have-a-way-to-render-a-loading-text-icon
http://www.slideshare.net/adamlogic/jquery-and-rails-sitting-in-a-tree
http://code.alexreisner.com/articles/link-to-remote-with-ujs.html