ios - Get current view controller from the app delegate (modal is possible)

Question

I know that to get the current view controller from the app delegate, I can use the navigationController property I have set up for my app. However, it's possible in many places throughout my app that a modal navigation controller could have been presented. Is there any way to detect this from the app delegate, since the current navigation controller will be different from the one to which the app delegate holds a reference?

Answer 1

Based on the gist here, I made a category to obtain the top most view controller, such that calling [[UIApplication sharedApplication] topMostViewController] will give you the top most view controller in your app.

This is especially useful in iOS 8 where UIAlertView and UIActionSheet have been deprecated in favor of UIAlertController, which needs to be presented on the top most view controller.

UIViewController+TopMostViewController.h

#import <UIKit/UIKit.h>

@interface UIViewController (TopMostViewController)

- (UIViewController *)topMostViewController;

@end

@interface UIApplication (TopMostViewController)

- (UIViewController *)topMostViewController;

@end

UIViewController+TopMostViewController.m

#import "UIViewController+TopMostViewController.h"

@implementation UIViewController (TopMostViewController)

- (UIViewController *)topMostViewController
{
    if (self.presentedViewController == nil)
    {
        return self;
    }
    else if ([self.presentedViewController isKindOfClass:[UINavigationController class]])
    {
        UINavigationController *navigationController = (UINavigationController *)self.presentedViewController;
        UIViewController *lastViewController = [[navigationController viewControllers] lastObject];
        return [lastViewController topMostViewController];
    }

    UIViewController *presentedViewController = (UIViewController *)self.presentedViewController;
    return [presentedViewController topMostViewController];
}

@end

#pragma mark -

@implementation UIApplication (TopMostViewController)

- (UIViewController *)topMostViewController
{
    return [self.keyWindow.rootViewController topMostViewController];
}

@end