iPhone - testing if a notification exists -

The code can add something at some point

  [[NSNotificationCenter defaultCenter] AddObserver: Self selector: @Selector (doSomething) Name: @ "hello" item: zero];  

How do I check whether this information is already activated or deleted in the queue, to prevent duplicates from being added?

Thank you.

If you mean "whether registered as a supervisor for notification" or not, then I do not think there is easier way to post notification and receive callbacks (with potentially devastating effects).

If there is a risk of double-ed, then I usually use the [[NSNotificationCenter defaultCenter] removeObserver: self name: foo object: bar] before adding.

Registration for notifications is not on a queue.