iphone - Does NSNotificationCenter removeObserver: deregister a VC from receiving MemoryWarning Notifications? -

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i stumbled issue in app: tested didreceivememorywarning calls uiviewcontroller including follow-up calls viewdidunload.

this used work fine in older versions of app, not working within iphone simulator: didreceivememorywarning not called more.

this caused calling [nsnotificationcenter defaultcenter] removeobserver:self] in viewwilldisappear (self being uiviewcontroller) unregister lifecycle notifications did add in viewdidappear.

that global removeobserver: call did not remove added notifications, apparently system's uiapplicationdidreceivememorywarningnotification notification caused uiviewcontroller's didreceivememorywarning being called.

is behaviour design? not find reference/document pointing out, calling removeobserver: within uiviewcontroller breaks standard memorywarning handling.

yes, design.

this behavior doesn't surprise me @ all. implementation of uiviewcontroller opaque there no way know sure registering instances uiapplicationdidreceivememorywarningnotification didreceivememorywarning action make sense.

as general rule, it's bad practice use [[nsnotificationcenter defaultcenter] removeobserver:self] anywhere in dealloc. because, you've discovered, there can unpredictable side effects in superclass implementations. it's more predictable , easier debug/maintain code if follow convention of unregistering specific notifications registered for.


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