iOS Objective-C 在当前显示的 UIAlertController 上获取参考

Question

I wanted to get a reference on the currently displayed UIAlertController .

(Some guys thought my question sucks and close voted it. However they were wrong, as there IS an answer to the question and I will post it, so others interested in this can find it!)

Answer 1

I've made a singleton class with one weak reference, then I've extended UIAlertController and made a new method to present it, where I set this weak reference to the newly displayed alert. Now this will hold the reference of the alert as long as it has any other reference, thus while it is displayed.

UIAlertController+Extension.h

@interface UIAlertController(Extension)

- (UIAlertController*)showIn:(UIViewController*)viewController;
+ (UIAlertController*)lastOnScreenAlert;

@end

UIAlertController+Extension.m

@interface LastAlert : NSObject

@property (nonatomic, weak) UIAlertController* reference;

@end

static LastAlert* lastAlert;

@implementation LastAlert

+ (void)initialize
{
    [super initialize];
    lastAlert = [LastAlert new];
}

@end

@implementation UIAlertController(Extension)

- (UIAlertController*)showIn:(UIViewController*)viewController
{
    [viewController presentViewController:self animated:YES completion:nil];
    [LastAlert class];
    lastAlert.reference = self;
    return self;
}
+ (UIAlertController*)lastOnScreenAlert
{
    return lastAlert.reference;
}

@end

Answer 2

There is a common solution to get the current alert controller that supports multiple windows and can work with third party libraries which present their own alerts:

static UIAlertController* currentAlertController() {
    for (UIWindow* window in UIApplication.sharedApplication.windows) {
        UIViewController* presented = window.rootViewController.presentedViewController;
        while (presented != nil) {
            if ([presented isKindOfClass:UIAlertController.class]) {
                return (UIAlertController *)presented;
            }
            presented = presented.presentedViewController;
        }
    }
    return nil;
}