ios - How to declare weak notification -

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maybe title not provide description please read following.

i have notification set listen event: 

nsnotificationcenter.defaultcenter().addobserver(self, selector: #selector(self.checkifnotificationswereturnedonafteralertshowing), name: uiapplicationwillenterforegroundnotification, object: uiapplication.sharedapplication())

then want remove observer on notification. found need use deinit this:

deinit  {      nsnotificationcenter.defaultcenter().removeobserver(uiapplicationwillenterforegroundnotification)     print("deinit") }

but problem when close view controller, program never executes deinit function. in answer found due strong reference.

i checked many links not able find how declare weak reference notification. how can declare weak notification?

hope question clear.

looking forward help.

i not able find way handle deinit decided remove observer in viewwilldisappear worked me. suggested rob napier in comment above


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