MVVM implementation with RxSwift and Realm - Two way binding - swift

Question

My implementation of the MVVM pattern with RxSwift, Realm and RxRealm looks like this:
E.g. I have a textfield that shows some editable content. I want this to be realtime saved/synched to the DB like this:
//View
textField.rx.text.subscribe(textViewModel.saveText.inputs)
viewModel.stringValue.drive(textField.rx.text)
//ViewModel:
lazy var saveText = Action<String,Void>{ newStringValue in
realm.write{
textObject.stringValue = newStringValue
}
//don't block the main thread
return Observable.just()
}
lazy var stringValue = Observable(from:textObject).map{$0.stringValue}.asDriver(onErrorJustReturn : "no string")
When typing slowly in the TextField, everything works accordingly. When typing very quickly thought, letters get "swallowed" like this:
Type "A"
write "A" to DB
Type "B"
Receive "A" from DB
-> Textfield value becomes A instead of AB.
When working with realtime synchronization this is the desired behaviour. For single text typing this seems not a good solution. How would such a 2-way binding be properly implemented and the undesired effect be avoided, especially in a scenario where the viewModel is processing the text value before write or after read from the source?

Answer 1

In your requirements will the Realm stored data ever be updated via another source? As in, could you ever receive a value in the string that came from another field?
If not, then you may be able to trust your input, and your writes can be eventually consistent.
The problem, though, comes down to the speed of writes and the notification returning the data; small but not nothing. Perhaps an intermediary would be beneficial.
For example, write your input field out to value that will periodically synchronise to Realm. That way your observable can have immediate access to the updated value and you can trust that eventually the value will be
Happy to explore further to see if we can solve something. :)
Edit:
Realm's guidance on conflict resolution.
A manual approach might be to hold two values; one is the value you start with, the other is the value that is being managed by the server.
If the starting value and the server value differ, you have a conflict to manage. Your strategy can be to reject one, accept one or somehow merge them, depending on the complexity of the data.