ios - Concern about memory when choosing between notification vs callback closure for network calls? -

many posts seem advise against notifications when trying synchronize functions, there other posts caution against closure callbacks because of potential inadvertently retain objects , cause memory issues.

assume inside custom view controller function, foo, uses bar class data server.

class customviewcontroller : uiviewcontroller {      function foo() {        // other stuff        // use bar data server        bar.getserverdata()      }  } 

option 1: define getserverdata accept callback. define callback closure inside customviewcontroller.

option 2: use nsnotifications instead of callback. inside of getserverdata, post nsnotification when server returns data, , ensure customviewcontroller registered notification.

option 1 seems desirable reasons people caution against nsnotification (e.g., compiler checks, traceability), doesn't using callback create potential issue customviewcontroller unnecessarily retained , therefore potentially creating memory issues?

if so, right way mitigate risk using callback, not using closure? in other words, define function inside customviewcontroller signature matching getserverdata callback, , pass pointer function getserverdata?

i'm going option 1 need remember of using [weak self] or whatever need 'weakify' in order avoid memory problems.

real world example:

filterrepository.getfiltersfortype(filtertype) { [weak self] (categories)  in     guard let strongself = self, categories = categories else { return }     strongself.datasource           = categories     strongself.filtereddatasource   = strongself.datasource     strongself.tableview?.reloaddata() } 

so in example can see pass reference self completion closure, weak reference. i'm checking if object still exists - if wasn't released already, using guard statement , unwrapping weak value.

definition of network call completion closure:

class func getfiltersfortype(type: filtertype, callback: ([filtercategory]?) -> ()) {     connection.getfilterscategories(type.id).response { (json, error) in         if let data = json {             callback(data.arrayvalue.map { filtercategory(attributes: $0) } )         } else {             callback(nil)         }     } }