有一个如何在WWDC 2010会话视频112中实现这个示例。如果您注册了iPhone开发人员程序，您可以从iTunes大学下载，如下所述。

There is a GREAT example of how to implement this in WWDC 2010 session video 112. If you are enrolled in the iPhone developer program, you can download it from iTunes University, as described below.

假设您在Apple开发者计划中，您收到了一封标题为WWDC for everyone的电子邮件。按照电子邮件中的链接，直到您访问iTunes大学。然后按照框架的链接，选择会话112.我认为实施大约在25分钟。

Assuming you are in the Apple Developer Program, you received an Email entitled "WWDC for everyone." Follow the links in that Email until you get to iTunes University. Then follow the link for frameworks, and pick session 112. I think the implementation is at approximately the 25 minute mark.