CODEWITHSUNDEEP
objective-cmacosnsnotificationcenternsviewcontroller
johnpurlia
johnpurlia

Reputation: 143

Observers remaining in dispatch table after object removed

Kind of a newbie question, so forgive me if I'm missing some basic concepts...

I have a view controller within a window, which contains multiple NSTableViews, each of which having a variety of associated observers added via addObserver. These work fine and as expected, with notifications going to each of the correct table views. However, if I close the window, then open a new window (of the same type), posted notifications are being sent to the table views of the window that was previously closed.

I was under the impression that as of macOS 10.11 observers did not have to be explicitly removed, which I would assume would happen when the original window is closed... UNLESS I'm missing something fundamental about closing windows. At the moment, I don't do anything special when the user closes a window, and the window just vanished from the screen. Do the views created in my viewDidLoad method live on even after the window is closed? Or no I need to explicitly dispose of these views in a method such as viewWIllDisappear?

Thanks!

Upvotes: 1

Views: 45

Answers (1)

Asperi
Asperi

Reputation: 257749

Even when object you added as observer is disposed the observer is not. According to official documentation you have to pair each addObserver with corresponding removeObserver. This is true and for NotificationCenter and for KVO. By the way adding object as observer does not increase its owners, so under correct memory management left observer result in run-time crash - that is why needed paired removeObserver (if there is no crash in such situation it means there is leak).

The place where to do this depends on usage. If you add observer in viewWillAppear then it is better to remove it in viewWillDisappear, if you add on creation then remove should be done in deinit

Upvotes: 1

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