Notifications not working on ModelContext

Question

Created Jun ’23

Replies 8

Boosts 3

Views 2.2k

Participants 8

I've been testing out SwiftData but haven't bee able to get ModelContext notifications working. I've tried both an objc observer and for await patterns but it never fires. If I listen for the older nsmanagedcontext notifications they are firing, but I am hoping that the new ones give an ID instead of an objectId. Has anyone got these working?

Attempt 1:

class NotificationObserver {
    init() {
        let didSaveNotification = ModelContext.didSave
        NotificationCenter.default.addObserver(self, selector: #selector(didSave(_:)),
                                               name: didSaveNotification, object: nil)
    }
    @objc func didSave(_ notification: Notification) {
        print(notification.name)
    }
}

Attempt 2:

class NotificationObserver {
    init() {
        let didSaveNotification = ModelContext.didSave
        Task {
            for await note in NotificationCenter.default.notifications(named: didSaveNotification) {
                print(note)
            }
        }
    }    
}

Boost

Answer 1

SpaceMan OP

Jun ’23

Your object is set to nil, but shouldn't it be set to ModelContext context?

0

Answer 2

SpaceMan OP

Jul ’23

Try this in your view controller to observe remote change notifications.

NotificationCenter.default.addObserver(self,
                           selector: #selector(updateView(_ :)),
                           name: .NSPersistentStoreRemoteChange,
                           object: nil)

0

Answer 3

vburojevic OP

Jul ’23

@pnewelljr any luck with this?

1

Answer 4

andrew48 OP

Aug ’23

facing same issue, anyone have any luck?

0

Answer 5

masterjefferson OP

Sep ’23

This seems to work:

NotificationCenter.default.notifications(named: Notification.Name.NSManagedObjectContextDidSave)

0

Answer 6

masterjefferson OP

Sep ’23

This works even better:

NotificationCenter.default.notifications(named: Notification.Name.NSManagedObjectContextObjectsDidChange)

Looks like a bug needs filed here. Appears that the NSManagedObjectContextObjectsDidChange is likely what ModelContext.didSave should be triggering, as the object in the notification is the ModelContext instance:

(lldb) po notif
▿ name = NSObjectsChangedInManagingContextNotification, object = Optional(SwiftData.ModelContext), userInfo = Optional([AnyHashable("updated"): Set([SwiftData.ModelContext.AnyPersistentObject(boxed: Redacted.Redacted)])])
  - name : "NSObjectsChangedInManagingContextNotification"
  ▿ object : <ModelContext: 0x281632e50>
  ▿ userInfo : 1 element
    ▿ 0 : 2 elements
      ▿ key : AnyHashable("updated")
        - value : "updated"
      ▿ value : 1 element
        ▿ 0 : AnyPersistentObject
          ▿ boxed : <Redacted: 0x280e545a0>

0

Answer 7

RFIHW OP

Sep ’24

I'm still encountering this issue and so confused there should not be an so obvious bug here.

Recently I decide to make App purely relying on SwiftData: 1. reading from network 2. write to context 3. only read data when notified without interrupting context writing.

For the notification object, I tried context, context.self, and even the actor calling the context.insert. None of them works.

Really need help!

0

Answer 8

malc OP

Nov ’24

This works for me on iOS 18.1

NSNotification.Name(rawValue: "_SwiftDataModelsChangedInContextNotificationPrivate"), object: modelContext)

0