Strange behavior of error tracking about activityindicator HOT 3 CLOSED

Yeah, you're right @hoc081098, that is how SwiftUI work. I understand that @huyparody get the sample code from README.md, it is my fault, it works perfectly in UIKit where the binding is invoked once, it would be a problem in SwiftUI as demonstrated. I'll update the README.md then.
Suggestion from @hoc081098 is perfect, I just wanna give @huyparody one more approach by using @Published

class ViewModel: ObservableObject {
...
@Published var errors: Errors?
init() {

   errorIndicator.errors
            .sink { error in self.errors = error }
            .store(in: &bag)
   }
...      
}      

Now you can use errors like other outputs such as isEnableLoginButton, it is more friendly with SwiftUI rather than Publisher
I'll close the issue, thank guys for the great discussion!

from activityindicator.

Hi @huyparody, thank for your report.
I can reproduce the issue from your sample project.
I just figure out if I sink the error publisher inside the ViewModel then the error publisher still works as expected.
I suppose the onReceive method of the View in the SwiftUI works unexpected, unfortunately I don't have much working experiences with SwifUI then I can't debug further. Hope you can help to figure it out from this point.

from activityindicator.

Every time ContentView.body is called, viewModel.errorPublisher will return a new Publisher instance (because it is a computed property).

That causes onReceive(_:perform:) to cancel the old Publisher and subscribe to the new one. The new one has the same behavior as ConcurrentValueSubject (aka. @Published private var relay: Error? ~ replay=1). So the latest error value is replayed the ContentView is rendered.

-> Avoid this by storing the Lazy Stored Properties that would persist between view re-renders.

class ViewModel: ObservableObject {
    lazy var errorPublisher: AnyPublisher<Error, Never> = errorIndicator.errors.eraseToAnyPublisher()
}

from activityindicator.