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? ...