[Office Hours] Shadowing Previous Outcomes for an updated Task

[dusixian]

In what area do you have a technical challenge?

Spezi Scheduler

Description

I’m working on a feature that notifies users if they haven’t recorded lab values for 7 days. This morning at 9 AM, I received a notification, and after entering a lab result, I closed and reopened the app. Upon relaunching, and open the schedule tab, I encountered the following error (the error won't show if I didn't open the schedule tab):

I checked the Spezi Scheduler repository and found that this error might occur in the createOrUpdateTask function. I suspect this happens because every time I reopen the app, the NeutroFeverGuardScheduler calls createOrUpdateTask. However, since my previous lab result marks future events as completed, creating or updating the task on app launch might unintentionally override those outcomes.

I’m wondering:

• Could the error occur because createOrUpdateTask runs every time I relaunch the app, unintentionally conflicting with already completed events?
• If so, how can I handle this properly? Should I check for existing completed events before recreating the task or handle it differently?

PR linked to the notification function.

Reproduction

Here’s how I implemented it:

1. I configure tasks in NeutroFeverGuardScheduler:

func configure() {
        do {
            try scheduler.createOrUpdateTask(
                id: "social-support-questionnaire",
                title: "Social Support Questionnaire",
                instructions: "Please fill out the Social Support Questionnaire every day.",
                category: .questionnaire,
                schedule: .daily(hour: 8, minute: 0, startingAt: .today) // you can change this to schedule stuff.
            ) { context in
                context.questionnaire = Bundle.main.questionnaire(withName: "SocialSupportQuestionnaire")
            }
            
            try scheduler.createOrUpdateTask(
                id: "enter-lab-result",
                title: "Enter Lab Results",
                instructions: "You haven't recorded your lab results for last 7 days. Record now!",
                category: .measurement,
                schedule: .daily(hour: 11, minute: 37, startingAt: .today),
                scheduleNotifications: true
            )
        } catch {
            viewState = .error(AnyLocalizedError(error: error, defaultErrorDescription: "Failed to create or update scheduled tasks."))
        }
    }

2. When a lab result is recorded, I complete future events within the next 7 days:

@MainActor
    func markRecentEventsAsComplete(_ recordTime: Date = Date()) {
        print("in markRecentEventsAsComplete")
        guard let sevenDaysLater = Calendar.current.date(byAdding: .day, value: 7, to: recordTime)
                                    else { return }
        
        do {
            let events = try scheduler.queryEvents(for: recordTime..<sevenDaysLater, predicate: #Predicate { $0.id == "enter-lab-result" })
            print("find event")
            print(events)
            for event in events {
                try event.complete()
                print("Marked event \(event.id) as complete")
            }
            scheduler.manuallyScheduleNotificationRefresh()
        } catch {
            print("Error querying or completing events: \(error)")
        }
    }

Expected behavior

No error.

Additional context

No response

Code of Conduct

• I agree to follow this course's Code of Conduct and Contributing Guidelines

[dusixian]

@lukaskollmer @PSchmiedmayer Hi! Could you take a look at this? This error occurs on my phone, and I can't reproduce it on the simulator (I don't know why)...

[lukaskollmer]

try specifying shadowedOutcomesHandling: .delete in the createOrUpdateTask call. we added this option in the latest release (1.2.0).

what this does is that when trying to update a task in a way that would cause issues with existing data that exist for upcoming event outcomes[^1], it will delete these upcoming outcomes, which allows you to update the task.

the reason why it probably seems to work fine in the simulator is because there's a longstanding SwiftData bug whereby changes to the ModelContext aren't auto-saved when running in the simulator. (when running on a real device, the autsave feature will work fine.)

also maybe have a look at my comment here, which goes into a little bit of detail regarding the different components of the Scheduler module, and how they interplay with each other; this should help explaining why there is a need in the first place to deal with potential shadowing of upcoming events/outcomes.

[^1] what does "upcoming event outcomes" mean? imagine having a task that is scheduled daily (ie, has one event per day), and you mark some of the upcoming events as completed. if you now change the task to have a weekly schedule, the database would still contain these completed daily events for the upcoming days. but they wouldn't match the task's schedule anymore. the option allows you to essentially tell the createOrUpdateTask function that you're fine with these outcomes for upcoming tasks being deleted from the database.

[lukaskollmer]

which branch? main?

[dusixian]

Yeah main.

[dusixian]

PR link: CS342/2025-NeutroFeverGuard#23
You can see file Schedule/NeutroFeverGuardScheduler.swift, and DataInputForm.swift/addLabResult(), I call markEventAsComplete in line 325.

[lukaskollmer]

i attemped to fix this in StanfordSpezi/SpeziScheduler#61. feel free to change the SpeziScheduler dependency in your app to the lukas/improve-shadowed-outcome-handling branch and give it a try 🚀

[dusixian]

Thank you so much!! Will try it and update you.

[dusixian]

Sorry for the late reply because I want to test on the phone for few days. It works now, thank you so much for your quick response!!!

[PSchmiedmayer]

Amazing; great to hear! 🚀