swift - Capturing self weak or unowned on asynchronous network requests -

whenever doing asynchronous network requests on arrival of request self nil (e.g. viewcontroller dismissed).

to prevent capturing self weak:

    future.onsuccess(context: queue.main.context, callback: { [weak self] result in         if let strongself = self {             // stuff self, guaranteed not nil             // strongself.somemethod()         }     }) 

or capture self unowned:

    future.onsuccess(context: queue.main.context, callback: { [unowned self] result in             // stuff self             // self.somemethod()     }) 

i not care request returning, because when request returning @ point in time when viewcontroller dismissed have nothing show request. not want keep self "alive" closure.

my question - enough capture self unowned in case? or have time nil checking [weak self]? happens in case of unowned capturing request when arrives , self nil - closure still alive , execute , trigger runtime error on accessing nil? or closure deallocated self , request run "void"?

or can forget both weak , unowned in case because when self get's deallocated closure deallocated , there no danger of accessing nil on arrival of request?

ps: know there many questions-answers on topic not find answer in case not care async arrival.

if capture self without weak or unowned keywords, view controller retained closure , not deallocate before closure dies. difference between weak , unowned weak optional , requires conditional binding safety check. on other hand, unowned not fail-safe. assumes view controller still alive , crash if not. more information see this answer.