I'm not sure if I got something wrong but from the examples I could find. I wrote that little helloworld.

#import <Foundation/Foundation.h>

#import <Foundation/NSUserNotification.h>





int main (int argc, const char * argv)

{

    NSUserNotification *userNotification = [[NSUserNotification alloc] init];

    userNotification.title = @"Some title";

    userNotification.informativeText = @"Some text";



    [[NSUserNotificationCenter defaultUserNotificationCenter] deliverNotification:userNotification];



    return 0;

}

I compile it with:

cc -framework Foundation -o app main.m

It compiles and I can execute it but it won't show anything. For some reasons, nothing gets presented. I read that Notifications may not get displayed if the application is the main actor. How can I make it show Notification?

set a delegate and override

- (BOOL)userNotificationCenter:(NSUserNotificationCenter *)center 

                               shouldPresentNotification:(NSUserNotification *)notification {

  return YES;

}

For a complete example in Objective-C and Swift:

We need to provide a NSUserNotificationCenterDelegate, in the simplest case we can use AppDelegate for this

Objective-C

We need to modify AppDelegate provide NSUserNotificationCenterDelegate method. From a clean AppDelegate (which looks like this...)

@interface AppDelegate ()

We'd modify it to be:

@interface AppDelegate () <NSUserNotificationCenterDelegate>

Now we can provide the required delegate method inside @implementation AppDelegate

- (BOOL)userNotificationCenter:(NSUserNotificationCenter *)center 

                               shouldPresentNotification:(NSUserNotification *)notification {

  return YES;

}

Swift 4

You can use an extension of AppDelegate to provide NSUserNotificationCenterDelegate methods:

extension AppDelegate: NSUserNotificationCenterDelegate {

    func userNotificationCenter(_ center: NSUserNotificationCenter, shouldPresent notification: NSUserNotification) -> Bool {

        return true

    }

}

I know it's an old question - but as there may be people looking for an answer how to do this in Python & PyObjC I will post the correct syntax here (as it's one of the top google results). As I can't comment on imp's comment I will post this as another answer.

It's possible to do the same in Python with pyobjc this way:

def userNotificationCenter_shouldPresentNotification_(self, center, notification):

    return True

Full class would look like this:

from Cocoa import NSObject

import objc



class MountainLionNotification(NSObject):

    """ MacOS Notifications """

    # Based on http://stackoverflow.com/questions/12202983/working-with-mountain-lions-notification-center-using-pyobjc



    def userNotificationCenter_shouldPresentNotification_(self, center, notification):

        return True



    def init(self):



        self = super(MountainLionNotification, self).init()

        if self is None: return None



        # Get objc references to the classes we need.

        self.NSUserNotification = objc.lookUpClass('NSUserNotification')

        self.NSUserNotificationCenter = objc.lookUpClass('NSUserNotificationCenter')



        return self



    def clearNotifications(self):

        """Clear any displayed alerts we have posted. Requires Mavericks."""



        NSUserNotificationCenter = objc.lookUpClass('NSUserNotificationCenter')

        NSUserNotificationCenter.defaultUserNotificationCenter().removeAllDeliveredNotifications()



    def notify(self, title="", subtitle="", text="", url=""):

        """Create a user notification and display it."""



        notification = self.NSUserNotification.alloc().init()

        notification.setTitle_(str(title))

        notification.setSubtitle_(str(subtitle))

        notification.setInformativeText_(str(text))

        # notification.setSoundName_("NSUserNotificationDefaultSoundName")

        notification.setHasActionButton_(False)

        notification.setActionButtonTitle_("View")

        # notification.setUserInfo_({"action":"open_url", "value": url})



        self.NSUserNotificationCenter.defaultUserNotificationCenter().setDelegate_(self)

        self.NSUserNotificationCenter.defaultUserNotificationCenter().scheduleNotification_(notification)



        # Note that the notification center saves a *copy* of our object.

        return notification

Be sure to assign a new identifier for any new notification. A notification will only show once, unless a new identifier is used or the user clears their notification history.