core data - CoreData: why not refresh UI if Buttons clicked

Question

Q1: Can '@Environment(.managedObjectContext) var context' monitor the changes of context? If not, it's just a method to get a value from environment, can I remove it, using CKDBManager.shared.context instead?

Q2: How can I refresh UI if some CoreData objects changed. One case is CoreData: why not refresh UI when book.isPublic toggled, the other two are following, how to fix them?

struct BookInfoView: View {
    @Environment(.managedObjectContext) var context
    var mySubscribe: Subscribe? {
        guard let subscribes = book.subscribes as? Set<Subscribe> else { return nil }
        return subscribes.first { $0.user?.id == Manager.shared.myId }
    }
    var isHidden: Bool {
        guard let subscribe = mySubscribe else { return false }
        return subscribe.isHidden
    }
    var isSubscribed: Bool {
        guard let subscribe = mySubscribe else { return false }
        return subscribe.isSubscribed
    }
    
    @ObservedObject var book: Book
    let viewType: ViewType
    
    var body: some View {
        print("refresh"); return
            VStack {
                Button(action: onHiddenToggled) {
                    Text(isHidden ? "show" : "hide")
                }

                Button(action: onSubscribeToggled) {
                    Text(isSubscribed ? "unsub" : "sub")
                }
            }
    }
    
    func onHiddenToggled() {
        guard let subscribe = mySubscribe else { return }
//        let ckdbManager = CKDBManager.shared
//        let context = ckdbManager.context
        context.perform {
            subscribe.isHidden.toggle()
            try? context.save()
        }
    }
    
    func onSubscribeToggled() {
        guard let subsribes = book.subscribes as? Set<Subscribe> else { return }

        let manager = Manager.shared
//        let ckdbManager = CKDBManager.shared
//        let context = ckdbManager.context
        context.perform {
            if let subscribe = subsribes.first(where: { $0.user?.id == manager.myId }) {
                subscribe.isSubscribed.toggle()
                try? context.save()
            } else {
                guard let myId = manager.myId else { return }
                let request: NSFetchRequest<User> = User.fetchRequest()
                request.predicate = NSPredicate(format: "id == %@", myId)
                guard let users = try? context.fetch(request), let user = users.first else { return }

                let subscribe = Subscribe(context: context)
                subscribe.book = book
                subscribe.user = user
                subscribe.subscribeAt = Date()
                subscribe.isHidden = false
                subscribe.isSubscribed = true

                try? context.save()
            }
        }
    }

question from:https://stackoverflow.com/questions/65651482/coredata-why-not-refresh-ui-if-buttons-clicked

Answer 1

Waitting for answers