Swipe to back not working滑动后退功能消失？

如果你发现滑动后退功能突然失效了，很可能是因为你隐藏了NavigationBar 或者定制了 leftBarButtonItem(s) 

这会导致 NavigationController 的 interactivePopGestureRecognizer 失去Delegate，所以滑动后退功能就消失了。你可以这样做：

self.navigationController.interactivePopGestureRecognizer.delegate = (id<UIGestureRecognizerDelegate>)self.navigationController;

参考：http://stackoverflow.com/questions/19054625/changing-back-button-in-ios-7-disables-swipe-to-navigate-back