NSUserNotificationCenter not showing notifications - nsusernotification

Question

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?

Answer 1

set a delegate and override
- (BOOL)userNotificationCenter:(NSUserNotificationCenter *)center
shouldPresentNotification:(NSUserNotification *)notification {
return YES;
}

Answer 2

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
}
}

Answer 3

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.

Answer 4

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

Answer 5

I followed the code on here but was unable to get a notification to work. It turned out that because I was on multiple monitors I needed to check the "When mirroring or sharing the display" option to get the alerts to present themselves. After that the python code worked.