IOS-指定返回Modal的控制器presentViewController
[self.presentingViewController.presentingViewController dismissViewControllerAnimated:NO completion:nil];
//如modal出来了两个视图控制器，就写两个presentingViewController
[self.presentingViewController.presentingViewController dismissViewControllerAnimated:NO completion:nil];
//如modal出来了两个视图控制器，就写两个presentingViewController