Get to UIViewController from UIView?

Question

Is there a built-in way to get from a UIView to its UIViewController? I know you can get from UIViewController to its UIView

Answer 1

There is no way.

What I do is pass the UIViewController pointer to the UIView (or an appropriate inheritance). I'm sorry I can't help with the IB approach to the problem because I don't believe in IB.

To answer the first commenter: sometimes you do need to know who called you because it determines what you can do. For example with a database you might have read access only or read/write ...

Answer 2

Combining several already given answers, I'm shipping on it as well with my implementation:

@implementation UIView (AppNameAdditions)

- (UIViewController *)appName_viewController {
    /// Finds the view's view controller.

    // Take the view controller class object here and avoid sending the same message iteratively unnecessarily.
    Class vcc = [UIViewController class];

    // Traverse responder chain. Return first found view controller, which will be the view's view controller.
    UIResponder *responder = self;
    while ((responder = [responder nextResponder]))
        if ([responder isKindOfClass: vcc])
            return (UIViewController *)responder;

    // If the view controller isn't found, return nil.
    return nil;
}

@end

The category is part of my ARC-enabled static library that I ship on every application I create. It's been tested several times and I didn't find any problems or leaks.

P.S.: You don't need to use a category like I did if the concerned view is a subclass of yours. In the latter case, just put the method in your subclass and you're good to go.

Answer 3

var parentViewController: UIViewController? {
    let s = sequence(first: self) { $0.next }
    return s.compactMap { $0 as? UIViewController }.first
}

Answer 4

Don't forget that you can get access to the root view controller for the window that the view is a subview of. From there, if you are e.g. using a navigation view controller and want to push a new view onto it:

    [[[[self window] rootViewController] navigationController] pushViewController:newController animated:YES];

You will need to set up the rootViewController property of the window properly first, however. Do this when you first create the controller e.g. in your app delegate:

-(void) applicationDidFinishLaunching:(UIApplication *)application {
    window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    RootViewController *controller = [[YourRootViewController] alloc] init];
    [window setRootViewController: controller];
    navigationController = [[UINavigationController alloc] initWithRootViewController:rootViewController];
    [controller release];
    [window addSubview:[[self navigationController] view]];
    [window makeKeyAndVisible];
}

Answer 5

Using the example posted by Brock, I modified it so that it is a category of UIView instead UIViewController and made it recursive so that any subview can (hopefully) find the parent UIViewController.

@interface UIView (FindUIViewController)
- (UIViewController *) firstAvailableUIViewController;
- (id) traverseResponderChainForUIViewController;
@end

@implementation UIView (FindUIViewController)
- (UIViewController *) firstAvailableUIViewController {
    // convenience function for casting and to "mask" the recursive function
    return (UIViewController *)[self traverseResponderChainForUIViewController];
}

- (id) traverseResponderChainForUIViewController {
    id nextResponder = [self nextResponder];
    if ([nextResponder isKindOfClass:[UIViewController class]]) {
        return nextResponder;
    } else if ([nextResponder isKindOfClass:[UIView class]]) {
        return [nextResponder traverseResponderChainForUIViewController];
    } else {
        return nil;
    }
}
@end

To use this code, add it into an new class file (I named mine "UIKitCategories") and remove the class data... copy the @interface into the header, and the @implementation into the .m file. Then in your project, #import "UIKitCategories.h" and use within the UIView code:

// from a UIView subclass... returns nil if UIViewController not available
UIViewController * myController = [self firstAvailableUIViewController];