Swift UI: Update view with random element from array

Question

I'm trying to update a view in Swift and I can't figure out how to make it work. My app has questions, which are loaded from Core data. From there, a random question should be displayed at the top. After saving the answer (by pressing the Button with action: save), a new random question should be displayed.

struct RecordView: View {
@Environment(\.managedObjectContext) var moc


@FetchRequest(entity: Question.entity(), sortDescriptors: [NSSortDescriptor(keyPath: \Question.question, ascending: false)])
var questions: FetchedResults<Question>
var currentQuestion: String { return questions.randomElement()!.question! }

@State private var newEntryText = ""


    var body: some View {
         VStack {
            Section(header: Text(currentQuestion)){
                       TextField("New entry", text: self.$newEntryText)
                        .padding(100)

                       HStack {
                           SwiftSpeech.RecordButton().scaleEffect(0.8).swiftSpeechToggleRecordingOnTap(locale: Locale(identifier: "de"), animation: .spring(response: 0.3, dampingFraction: 0.5, blendDuration: 0))
                               .onRecognize(update: self.$newEntryText)

                        Button(action: save)
                           {
                            Image(systemName: "plus.circle.fill").foregroundColor(.green).imageScale(.large).scaleEffect(2.0)
                               }

                       }
                   }.automaticEnvironmentForSpeechRecognition()
    }
}

    func save() {
        let newEntry = Entry(context: self.moc)
             newEntry.text = self.newEntryText
             newEntry.createdAt = Date()
        do {
            try self.moc.save()
        }catch{
            print(error)
        }
        self.newEntryText = ""
        print(currentQuestion)

    }

What I tried:

1) @State var currentQuestion: String = questions.randomElement()!.question!-> Cannot use instance member 'questions' within property initializer; property initializers run before 'self' is available. Here the problems seems to be that the questions array has to be loaded first.
2) var currentQuestion: String { return questions.randomElement()!.question! } -> Here the currentQuestion is recomputed every time it is accessed, but the View does not update. Same thing if I move the questions.randomElement()!.question! to the Text() component.
3) lazy var currentQuestion = questions.randomElement()!.question!-> Cannot use mutating getter on immutable value: 'self' is immutable (at the Text() component). The lazy part should have solved the problem I have at the 1) solution, but then I cannot use it at the Text() component.

... and some other minor variations. I'm a Swift/Swift UI Beginner, and I am running out of ideas how to update the displayed current question everytime the button is pressed. Does anyone has an idea for this?
Many thanks!

Asperi · Accepted Answer · 2020-05-30 11:14:59Z

2

Try the following (scratchy)

@State var currentQuestion: String = "" // as state !!

var body: some View {
    VStack {
        Section(header: Text(currentQuestion)){

           // ... other your code here

        }.automaticEnvironmentForSpeechRecognition()
    }.onAppear {
        self.nextQuestion()    // << here !!
    }
}

...

func save() {
    // ... other your code here

   self.nextQuestion()         // << here !!
}

private func nextQuestion() {
   self.currentQuestion = questions.randomElement()?.question ?? ""
}

answered May 30, 2020 at 11:14

Asperi

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