Firebase数据库不会脱机返回值

Question

I'm working on a app with Firebase Database and I also want to allow the user adding entries when he's offline. Imagine the following case (everything offline; it works perfectly online):

1. The user adds a client (shown in a main tableview - works)
2. On the detail view of the freshly added client, he adds an appointment with him. The appointments are listed in a tableview in the Client Detail ViewController.
3. When the appointment is added, the tableview isn't refreshed, because the callback doesn't call.

In code:

1. navCont.child = userDB.child(entityNameClients).childByAutoId() navCont.child?.setValue(post) where post is a dictionary with the values of the customer
2. On the viewDidLoad Method of the detail view controller, I call the following code: getUsersDBReference().child(entityNameAppointments).child(clientKey).observe(.value) . The Callback isn't called (probably because there are no elements in it)

3. Adding Appointment

    var appointment:DatabaseReference 

   appointment = getUsersDBReference().child(entityNameAppointments).child(clientKey).childByAutoId() appointment.setValue(appointmentDict)

4. The Callback of 2 isn't called (--> and the tableview not refreshed with the new appointment)

BTW, I set Database.database().isPersistenceEnabled = true in App Delegates applicationDidLoad -method. And if I add the client online and go offline then, it works too.

Answer 1

Answer of Firebase Support:

The SDK attempts not to fire Value events with "partial" data. Since you are only updating a subnode of the location being observed, we don't have "complete" data and so the observer is not fired. If the SDK has ever had "complete" data for that node (eg because you overwrote the whole node or because you were previously online and got complete data for it), then it will fire events when you update it.

One workaround would be to use ChildAdded (and ChildChanged, etc.) events instead of Value.