How can I find the UIPopoverController from the UIViewController being displayed in a popover?

votes

Using an instance of a UIViewController, is there any way I can find the UIPopoverController being used to present it? I would also want to find the UIViewController that displayed the UIPopoverController in the first place.

I would normally use a delegate or other sort of notification to send a signal from the displayed view controller to the displaying one, but in this case I'm trying to create a reusable custom segue that dismisses the popover and then moves on to another view in the main view.

iosipadpopover

Why don't you give the answer below the magic checkmark? – David H

6 Answers

votes

You would think that this would be simple (the UIViewController even has a private _popoverController property!), but it is not.

The general answer is that you have to save a reference to the UIPopoverController in the UIViewController that it is presenting, at the time the UIViewController is created.

If you are creating the UIPopoverController programmatically, then that's the time to store the reference in your UIViewController subclass.
If you are using Storyboards and Segues, you can get the UIPopoverController out of the segue in the prepareForSegue method:
```
UIPopoverController* popover = [(UIStoryboardPopoverSegue*)segue popoverController];
```

Of course, be sure that your segue really is a UIStoryboardPopoverSegue!

votes

My recommendation is to leverage a combination of your own custom property and the private APIs in UIKit. To avoid app store rejection, any private APIs should compile out for release builds, and should be used only to check against your implementation.

First let's build the custom property into a category on UIViewController. This allows some perks in the implementation, and it doesn't require you to go back and derive every class from some custom view controller subclass.

// UIViewController+isPresentedInPopover.h

#import <UIKit/UIKit.h>

@interface UIViewController (isPresentedInPopover)

@property (assign, nonatomic, getter = isPresentedInPopover) BOOL presentedInPopover;

@end

Now for the implementation - we'll be using the Objective C runtime's associated object API to provide the storage for this property. Note that a selector is a nice choice for the unique key used to store the object, as it's automatically uniqued by the compiler and highly unlikely to be used by any other client for this purpose.

// UIViewController+isPresentedInPopover.m

#import "UIViewController+isPresentedInPopover.h"
#import <objc/runtime.h>

@implementation UIViewController (isPresentedInPopover)

- (void)setPresentedInPopover:(BOOL)presentedInPopover
{
    objc_setAssociatedObject(self,
                             @selector(isPresentedInPopover),
                             [NSNumber numberWithBool:presentedInPopover],
                             OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (BOOL)isPresentedInPopover
{
    NSNumber *wrappedBool = objc_getAssociatedObject(self, @selector(isPresentedInPopover));
    BOOL userValue = [wrappedBool boolValue];
    return userValue ?: [[self parentViewController] isPresentedInPopover];
}

@end

So there's a convenient side effect of using this as a category - you can call up to the parentViewController and see if that is contained in a popover as well. This way you can set the property on, say, a UINavigationController and all of its child view controllers will respond correctly to isPresentedInPopover. To accomplish this with subclasses, you'd be either trying to set this on every new child view controller, or subclassing navigation controllers, or other horrific things.

More Runtime Magic

There is still more that the Objective C Runtime has to offer for this particular problem, and we can use them to jump into Apple's private implementation details and check your own app against it. For release builds, this extra code will compile out, so no need to worry about the all-seeing eye of ~~Sauron~~ Apple when submitting to the store.

You can see from UIViewController.h that there is an ivar defined as UIPopoverController* _popoverController with @package scope. Luckily this is only enforced by the compiler. Nothing is sacred as far as the runtime is concerned, and it's pretty easy to access that ivar from anywhere. We'll add a debug-only runtime check on each access of the property to make sure we're consistent.

// UIViewController+isPresentedInPopover.m

#import "UIViewController+isPresentedInPopover.h"
#import <objc/runtime.h>

@implementation UIViewController (isPresentedInPopover)

- (void)setPresentedInPopover:(BOOL)presentedInPopover
{
    objc_setAssociatedObject(self,
                             @selector(isPresentedInPopover),
                             [NSNumber numberWithBool:presentedInPopover],
                             OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (BOOL)isPresentedInPopover
{
    NSNumber *wrappedBool = objc_getAssociatedObject(self, @selector(isPresentedInPopover));
    BOOL userValue = [wrappedBool boolValue];

#if DEBUG
    Ivar privatePopoverIvar = class_getInstanceVariable([UIViewController class], "_popoverController");
    UIPopoverController *popover = object_getIvar(self, privatePopoverIvar);
    BOOL privateAPIValue = popover != nil;

    if (userValue != privateAPIValue) {
        [NSException raise:NSInternalInconsistencyException format:
         @"-[%@ %@] "
         "returning %@ "
         "while private UIViewController API suggests %@. "
         "Did you forget to set 'presentedInPopover'?",
         NSStringFromClass([self class]), NSStringFromSelector(_cmd),
         userValue ? @"YES" : @"NO",
         privateAPIValue ? @"YES" : @"NO"];
    }
#endif

    return userValue ?: [[self parentViewController] isPresentedInPopover];
}

@end

When using the property incorrectly, you'll get a message like this on the console:

2012-09-18 14:28:30.375 MyApp[41551:c07] * Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Consistency error in -[UINavigationController isPresentedInPopover]: returning NO while private UIViewController API suggests YES. Did you forget to set 'presentedInPopover'?'

...but when compiling with the DEBUG flag off or set to 0, it compiles down to the exact same code as before.

For The Free and the Foolhardy

Maybe you're doing Ad-Hoc/Enterprise/personal builds, or you're sufficiently bold to see just what Apple thinks about this one for the App Store. Either way, here's an implementation that just works using the current runtime and UIViewController - no setting properties needed!

// UIViewController+isPresentedInPopover.h

#import <UIKit/UIKit.h>

@interface UIViewController (isPresentedInPopover)

@property (readonly, assign, nonatomic, getter = isPresentedInPopover) BOOL presentedInPopover;

@end

// UIViewController+isPresentedInPopover.m

#import "UIViewController+isPresentedInPopover.h"
#import <objc/runtime.h>

@implementation UIViewController (isPresentedInPopover)

- (BOOL)isPresentedInPopover
{
    Ivar privatePopoverIvar = class_getInstanceVariable([UIViewController class], "_popoverController");
    UIPopoverController *popover = object_getIvar(self, privatePopoverIvar);
    BOOL privateAPIValue = popover != nil;
    return privateAPIValue ?: [[self parentViewController] isPresentedInPopover];
}

@end

votes

Most helpful would probably be to make popover a class variable, so in the .m file of the class that is going to present the popover, do something like this:

    @interface ExampleViewController()
    @property (nonatomic, strong) UIPopoverController *popover
    @end

    @implementation
    - (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
    {
        if ([segue.identifier isEqualToString:@"some segue"])
        {
            //prevent stacking popovers
            if ([self.popover isPopoverVisible])
            {
                [self.popover dismissPopoverAnimated:YES];
                self.popover = nil;
            }
            [segue.destinationViewController setDelegate:self];
            self.popover = [(UIStoryboardPopoverSegue *)segue popoverController];
         }
     }
     @end

votes

As @joey wrote above, Apple eliminated the need for the dummy control in iOS 8 with the popoverPresentationController property defined for UIViewController as the "The nearest ancestor in the view controller hierarchy that is a popover presentation controller. (read-only)".

Here is an example in Swift for a UIPopoverPresentationController-based segue defined on a storyboard. In this case, a button has been added programmatically and can be defined in this way as the pop-over's anchor. The sender could also be a selected UITableViewCell or a view from it.

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    if segue.identifier == "showCallout" {
        let button = sender as UIButton
        let calloutViewController = segue.destinationViewController as CalloutViewController
        if let popover = calloutViewController.popoverPresentationController {
            popover.sourceView = button
            popover.sourceRect = button.bounds
        }
    }
}

votes

Taking off from ndoc's anwser: this answer shows a neater way in iOS 6 to prevent a popover from showing multiple time through segues. The method in the link was the one that worked awesomely for me for preventing popover stacking.

-1

votes

If you JUST want to know if your controller is being presented inside a popover (not interested to get a reference to the popover controller), you can simply do this, without storing variables nor hacking private API's.

-(BOOL)isPresentedInPopover
{
    for (UIView *superview = self.view.superview; superview != nil; superview = superview.superview)
    {
        if ([NSStringFromClass([superview class]) isEqualToString:@"_UIPopoverView"])
            return YES;
    }
    return NO;
}