#Published variable causes crash without didSet - swiftui

Question

I have an ObservableObject view model with a #Published variable that's an enum indicating the status of the viewModel:
class BatchesViewModel: ObservableObject {
#Published private var lookupStatus: BatchLookupStatus = .none
...
}
enum BatchLookupStatus {
case none
case lookingUp(searchText: String)
case error(errorMessage: String)
case validated(batch: Batch)
}
I set the status when there's an error, or there's a validation, etc. I set the status back to .none when the error is dismissed.
Everything works fine, except I get a EXC_BAD_ACCESS crash randomly.
I wanted to see what the status was when that happens, so I put a print statement when the status is set:
#Published private var lookupStatus: BatchLookupStatus = .none {
didSet {
print(_lookupStatus)
}
}
I noticed that with that print statement, the crash no longer happens. In fact, if I just leave an empty didSet, it prevents the crash as well:
#Published private var lookupStatus: BatchLookupStatus = .none { didSet {} }
As soon as I remove the didSet, it crashes again.
What in the world is going on?

Answer 1

I assume the reason is not in the provided model, because as tested it all works as expected - I mean with Published-Refresh flow.
Here is an example of your model usage I did:
import SwiftUI
import Combine
class BatchesViewModel: ObservableObject {
#Published var lookupStatus: BatchLookupStatus = .none
}
enum BatchLookupStatus {
case none
case lookingUp(searchText: String)
case error(errorMessage: String)
}
struct TestPublishCrashed: View {
#ObservedObject var viewModel = BatchesViewModel()
var body: some View {
VStack {
Button(action: {
self.viewModel.lookupStatus = .error(errorMessage: "Search failed")
}) {
Text("Emulate Error").padding().background(Color.yellow)
}.padding()
Button(action: {
self.viewModel.lookupStatus = .lookingUp(searchText: "hello world")
}) {
Text("Emulate Query").padding().background(Color.yellow)
}.padding()
status.padding()
}
}
var status: some View {
switch viewModel.lookupStatus {
case .none:
return Text("No status")
case .error(let error):
return Text("Got error: \(error)")
case .lookingUp(let query):
return Text("Searching: \(query)")
}
}
}
struct TestPublishCrashed_Previews: PreviewProvider {
static var previews: some View {
TestPublishCrashed()
}
}