CODEWITHSUNDEEP
iosnsnotificationcenternsnotificationsnsnotification
cdub
cdub

Reputation: 25701

Proper way to listen to NSNotifications

Is it proper, if I have 2 notifications on a view controller to have 2 observers like so:

[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(handleNotifications:) name:@"note1" object:nil];
[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(handleNotifications:) name:@"note2" object:nil];

Or do I just figure out which notification was run by passing in nil to the name and then checking the notification sent in the handleNotification function:

[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(handleNotifications:) name:nil object:nil];

Thanks.

Upvotes: 0

Views: 231

Answers (1)

Cyrille
Cyrille

Reputation: 25144

Actually, if you pass nil as a name, you'll receive all notifications regardless of their name (not just the two you want). It's better to subscribe to each one separately, by naming them.

Excerpt from Apple documentation:

If you pass nil, the notification center doesn’t use a notification’s name to decide whether to deliver it to the observer.

(That point was, at first, not clear to me and I misread it by thinking you would not receive any notification).

You can use the same callback/listener for both, and decide what to do based on the notification received.

You could create a category on NSNotificationCenter to handle the registration of multiple names, that's what categories are made for!

Upvotes: 4

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