NSTableViewDelegate receiving multiple NSNotifications

Question

I have a view-based NSTableView whose data is supplied by a subclass of NSArrayController. The array controller also receives NSNotifications (just 2) from other objects telling it to update. As long as the array controller is not acting as a delegate for the NSTableView, everything works as expected and each notification is received only once. When I attach the array controller as a delegate for the NSTableView (in IB), these same notifications are received multiple (like hundreds!) of times. The array controller is only registered once for these notifications (in awakeFromNib:).

score 2 · Answer 1 · answered Mar 03 '14 at 06:46

2

Notifications and delegates are two independent mechanisms in Cocoa.

There must be something else going on in your code as attaching delegates shouldn't alter the number/kinds of notifications being received.

answered Mar 03 '14 at 06:46

Jay

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Thanks, Jay. That's what has me baffled. It is code that worked beautifully on a previous version, but is now broken. The only substantive change is from cell-based to view-based NSTableView. I'll keep digging. – Joel Mar 03 '14 at 08:34

Joel · Accepted Answer · 2014-03-18T16:10:18.010

For the sake of posterity.

In Apple's 'Table View Programming Guide for Mac' is this little nugget:

Note: Calling makeViewWithIdentifier:owner: causes awakeFromNib to be called multiple times in your app. This is because makeViewWithIdentifier:owner: loads a NIB with the passed-in owner, and the owner also receives an awakeFromNib call, even though it’s already awake.

So, when attached as a delegate, my class' awakeFromNib: was being called for every visible NSTableView cell, resulting in the notification observer being registered each time.

NSTableViewDelegate receiving multiple NSNotifications

2 Answers2