[self dismissViewControllerAnimated:YES completion:^{

        // 这是从一个模态出来的页面跳到tabbar的某一个页面

        AppDelegate *appDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];

        UITabBarController *tabViewController = (UITabBarController *) appDelegate.window.rootViewController;

        [tabViewController setSelectedIndex:];

    }];