Hello dear swiftui learners;-)

I have been trying to create a simple workout application, hovever it seems I have skipped some basics and can't make my views update on property change

here is my code:

import SwiftUI

@main
struct TestAppApp: App {
@StateObject var manager = HealthKitManager()
    var body: some Scene {
        WindowGroup {
            ContentView()
                .environmentObject(manager)
        }
    }
}

struct ContentView: View {
    @EnvironmentObject var manager: HealthKitManager

    var body: some View {
        ScrollView {
            ForEach(manager.activities.sorted(by: {$0.value.id < $1.value.id}), id: \.key) { item in
                ActivityCard(activity: item.value)
            }
        }
        .refreshable {
            manager.update()
        }
    }
}

struct Activity: Identifiable {
    var id: Int
    var title: String
    var amount: Int
}

struct ActivityCard: View {
    @State var activity: Activity
    var body: some View {
        VStack {
            Text(activity.title)
            Text("\(activity.amount)")
        }
    }
}

class HealthKitManager: ObservableObject {
    @Published var activities: [String : Activity] = [
        "steps": Activity(id: 1, title: "Steps", amount: 0),
        "calories": Activity(id: 2, title: "Calories", amount: 0)
    ]

    func update() {
        let activity = Activity(id: 3, title: "Distance", amount:  10)
        self.activities["distance"] = activity // this work
        self.activities["steps"]?.amount = 10 // this does not!
        print(self.activities) // but it's updated
    }
}

if I add new activity to activities it will work, but if i try to update property of existing activity it's no luck.

chatgpt suggested to change struct to class - not working

class Activity: Identifiable, ObservableObject {
    var id: Int
    var title: String
    @Published var amount: Int

    init(id: Int, title: String, amount: Int) {
        self.id = id
        self.title = title
        self.amount = amount
    }
}

another suggestion was objectWillChange.send() - not working

        objectWillChange.send()
        self.activities["steps"]?.amount = 10
        objectWillChange.send()

I have been trying everything, can somebody please help me?

thank you!

Peter

@Peter is stuck and offered this observation:

hovever it seems I have skipped some basics .....

Yes! Yes you have.

I wonder where you learned about @ObservableObject and @Published? Did you learn these techniques from the 100 Days of SwiftUI course that's available free on this terrific web site?

for these interested.. https://www.hackingwithswift.com/books/ios-swiftui/sharing-swiftui-state-with-observable answers my question if I understand it right

@Observable
class Activity: Identifiable {
    var id: Int
    var title: String
    var amount: Int

    init(id: Int, title: String, amount: Int) {
        self.id = id
        self.title = title
        self.amount = amount
    }
}

func update() {
      var activity = Activity(id: 3, title: "Distance", amount:  10)

      self.activities["distance"] = activity // this works
      self.activities["steps"]?.amount = 100 // this now works too!

      var act = Activity(id: 1, title: "Steps", amount:  20)
      self.activities["steps"]=act // not working

      self.activities.removeValue(forKey: "steps") // also not working
      // previous removeValue would work without next line = MAGIC! ;-)
      self.activities["steps"]=act

      print("\(self.activities["steps"]?.amount ?? 0)")
  }

can't help myself but I am finding swift and especially swiftUI too magic for my taste

can somebody please explain me what is going on?