ALTAPPS-542: [Shared, iOS] topics completion

[vladkash]

YouTrack Issues:
#ALTAPPS-542

Checklist

Before Code Review:

• Fields "Assignees, Labels, Milestone" are filled in the pull request;
• Sentry Performance Monitoring of screen loading is added for new screens;
• View analytics events are added for new screens;
• New analytics events are documented;
• All checks have been passed;
• Changes have been checked locally.

Description

Start practicing button flow

StepCompletionFeature.Message.StartPracticingClicked (via StepFeature.Message.StepCompletionMessage) -> StepCompletionFeature.Action.FetchNextStepQuiz -> StepCompletionFeature.Message.NextStepQuizFetchedStatus.(Success|Error) -> StepCompletionFeature.Action.ViewAction.(ReloadStep|ShowPracticingErrorStatus) (via StepFeature.Action.ViewAction.StepCompletionViewAction)

Continue button flow

StepCompletionFeature.Message.ContinuePracticingClicked (via StepFeature.Message.StepCompletionMessage) -> (StepCompletionFeature.Action.FetchNextStepQuiz | StepCompletionFeature.Action.ViewAction.NavigateTo.Back | StepCompletionFeature.Action.ViewAction.NavigateTo.HomeScreen) -> StepCompletionFeature.Message.NextStepQuizFetchedStatus.(Success|Error) -> StepCompletionFeature.Action.ViewAction.(ReloadStep|ShowPracticingErrorStatus) (via StepFeature.Action.ViewAction.StepCompletionViewAction)

Checking topic completion

notificationInteractor.solvedStepsSharedFlow -> StepCompletionFeature.Message.StepSolved -> StepCompletionFeature.Action.CheckTopicCompletion -> StepCompletionFeature.Message.CurrentTopicStatus.(Completed | Uncompleted) -> StepCompletionFeature.Action.ViewAction.ShowTopicCompletedModal (via StepFeature.Action.ViewAction.StepCompletionViewAction)

Minor changes

• Added BlockName.supportedBlocksNames extension to manage different supported step types on both platforms
• Added new methods and renamed SwiftUIPushRouter -> SwiftUIStackRouter to implement necessary navigation on iOS

[ivan-magda]

@ivan-magda there is one problem left with @Published var isPracticingLoading in StepQuizViewModel we discussed

@vladkash the problem was that when the "Start Practicing" or "Continue" buttons were tapped it updated StepFeature.State which produces an update of the StepViewModel and StepQuizViewModel and its recreation (new instances are created), so StepViewModel.stepQuizModuleInput has incorrect reference. I updated the callback that provides stepQuizModuleInput, which resolves the issue. I don't know why SwiftUI recreates StepViewModel and StepQuizViewModel on the view model state update, we are using the @StateObject property wrapper to avoid this.

You can print the pointer address of the view model using this code:

let address = Unmanaged<AnyObject>.passUnretained(viewModel).toOpaque()
let _ = print("address of ViewModel = \(address)")

Also, when I debugged this issue I found that we have retained cycles, when SwiftUI View disappears its view model not deallocates. For example, suppose something like:

class MyObject {
    var function = { () }
}

struct MyStruct {
    let obj = MyObject()

    func structMethod() { ... }
    init() {
        obj.function = { structMethod() }
    }
}

The closure will capture self, which retains obj, which retains the closure, so this forms a retain cycle. We have the same situation with our handling of the view actions in the SwiftUI views, to fix this we need directly clear onViewAction callback to break the retain cycle.

I'll take one last look at the PR and we'll be ready to merge it.