如何进行测试
1. 在模拟器里，点击 Hardware > Simulate Memory Warning to test. 那么我们整个程序每个页面就都能够支持这个功能了。
2. Be sure to test your app in Airplane Mode.
Access properties/methods in other classes
One way to do this is via the AppDelegate:
myAppDelegate *appDelegate = (myAppDelegate *)[[UIApplication sharedApplication] delegate]; [[[appDelegate rootViewController] flipsideViewController] myMethod];
