How to properly use CFNotificationCenterAddObserver in Swift for iOS

Pulling my hair out getting CFNotificationCenterAddObserver to work in Swift.

        CFNotificationCenterAddObserver(CFNotificationCenterGetDarwinNotifyCenter(),
        UnsafePointer<Void>(self),
        iosLocked,
        "com.apple.springboard.lockcomputer" as CFString,
        nil,
        CFNotificationSuspensionBehavior.DeliverImmediately)

The iOS docs have it listed and I have tried countless iterations on the callback and the unsafe pointer with no success.

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  • The above function call results in this error message, which seems to be the correct init:

    Cannot invoke 'init' with an argument list of type '(CFNotificationCenter!, $T4, () -> (), CFString, NilLiteralConvertible, CFNotificationSuspensionBehavior)'
    

    I also tried bridging to objc as this post here suggests, but without success.

    Here is my bridge:

    LockNotifierCallback.h:

    #import <Foundation/Foundation.h>
    
    @interface LockNotifierCallback : NSObject
    
    + (void(*)(CFNotificationCenterRef center, void *observer, CFStringRef name, const void *object, CFDictionaryRef userInfo))notifierProc;
    
    @end
    

    and LockNotifierCallback.m:

    #import "LockNotifierCallback.h"
    
    static void lockcompleteChanged(CFNotificationCenterRef center, void *observer, CFStringRef name, const void *object, CFDictionaryRef userInfo) {
        NSLog(@"success");
    }
    
    @implementation LockNotifierCallback
    
    
    + (void(*)(CFNotificationCenterRef center, void *observer, CFStringRef name, const void *object, CFDictionaryRef userInfo))notifierProc {
        return lockcompleteChanged;
    }
    
    @end
    

    with updated CFNotificationCenterAddObserver call as follows:

    CFNotificationCenterAddObserver(CFNotificationCenterGetDarwinNotifyCenter(),
            LockNotifierCallback.notifierProc,
            iosLocked,
            "com.apple.springboard.lockcomputer" as CFString,
            nil,
            CFNotificationSuspensionBehavior.DeliverImmediately)
    

    and of course LockNotifierCallback.h is in my Bridging header. Error continues:

    Cannot convert the expression's type '(CFNotificationCenter!, () -> CFunctionPointer<((CFNotificationCenter!, UnsafeMutablePointer<Void>, CFString!, UnsafePointer<Void>, CFDictionary!) -> Void)>, () -> (), CFString, NilLiteralConvertible, CFNotificationSuspensionBehavior)' to type 'StringLiteralConvertible'
    

    Solutions Collect From Internet About “How to properly use CFNotificationCenterAddObserver in Swift for iOS”

    I had some issues with DarwinNotifications, you can try using this wrapper class
    just include header file in your bridging file. And you can use it in swift.

    DarwinNotificationsManager.h :

    #import <Foundation/Foundation.h>
    
    #ifndef DarwinNotifications_h
    #define DarwinNotifications_h
    
    @interface DarwinNotificationsManager : NSObject
    
    @property (strong, nonatomic) id someProperty;
    
    + (instancetype)sharedInstance;
    
    - (void)registerForNotificationName:(NSString *)name callback:(void (^)(void))callback;
    - (void)postNotificationWithName:(NSString *)name;
    
    @end
    
    #endif
    

    DarwinNotificationsManager.m :

    #import <Foundation/Foundation.h>
    #import "DarwinNotificationsManager.h"
    
    
    @implementation DarwinNotificationsManager {
        NSMutableDictionary * handlers;
    }
    
    + (instancetype)sharedInstance {
        static id instance = NULL;
        static dispatch_once_t onceToken;
        dispatch_once(&onceToken, ^{
            instance = [[self alloc] init];
        });
        return instance;
    }
    
    - (instancetype)init {
        self = [super init];
        if (self) {
            handlers = [NSMutableDictionary dictionary];
        }
        return self;
    }
    
    - (void)registerForNotificationName:(NSString *)name callback:(void (^)(void))callback {
        handlers[name] = callback;
        CFNotificationCenterRef center = CFNotificationCenterGetDarwinNotifyCenter();
        CFNotificationCenterAddObserver(center, (__bridge const void *)(self), defaultNotificationCallback, (__bridge CFStringRef)name, NULL, CFNotificationSuspensionBehaviorDeliverImmediately);
    }
    
    - (void)postNotificationWithName:(NSString *)name {
        CFNotificationCenterRef center = CFNotificationCenterGetDarwinNotifyCenter();
        CFNotificationCenterPostNotification(center, (__bridge CFStringRef)name, NULL, NULL, YES);
    }
    
    - (void)notificationCallbackReceivedWithName:(NSString *)name {
        void (^callback)(void) = handlers[name];
        callback();
    }
    
    void defaultNotificationCallback (CFNotificationCenterRef center,
                     void *observer,
                     CFStringRef name,
                     const void *object,
                     CFDictionaryRef userInfo)
    {
        NSLog(@"name: %@", name);
        NSLog(@"userinfo: %@", userInfo);
    
        NSString *identifier = (__bridge NSString *)name;
        [[DarwinNotificationsManager sharedInstance] notificationCallbackReceivedWithName:identifier];
    }
    
    
    - (void)dealloc {
        CFNotificationCenterRef center = CFNotificationCenterGetDarwinNotifyCenter();
        CFNotificationCenterRemoveEveryObserver(center, (__bridge const void *)(self));
    }
    
    
    @end
    

    In swift you can use it like this :

    let darwinNotificationCenter = DarwinNotificationsManager.sharedInstance()
    darwinNotificationCenter.registerForNotificationName("YourNotificationName"){
                //code to execute on notification
    }