Animates wrongly at every switch of direction, animates right in same direction

SwiftUI remembers the "old" view in order to perform a transition to the "new" view. When you reverse direction, the outgoing view is still associated with a transition going in the (now) wrong direction. My fix is to immediately change the direction when you press the button. This causes body() to be re-invoked, but no transition is visible because the view ID of the question has not changed. Subsequently, a Task alters the view ID, which causes a transition from the old question (now associated with a removal transition in the new direction) to the new question.

I think this solution smells a little, because it is imperatively driving the UI, and because I have no idea when the Task closures will actually be invoked. No doubt after the Button's action closure, but are they guaranteed to be invoked before any subsequent UI action? I don't know.

I changed QuizView to ContentView to get it to compile in my test app.

import SwiftUI
 
struct Question {
    let id: Int
    let text: String
}
extension AnyTransition {
    static var slideRight: AnyTransition {
        let insertion = AnyTransition.move(edge: .trailing)
        let removal = AnyTransition.move(edge: .leading)
        return .asymmetric(insertion: insertion, removal: removal)
    }
    
    static var slideLeft: AnyTransition {
        let insertion = AnyTransition.move(edge: .leading)
        let removal = AnyTransition.move(edge: .trailing)
        return .asymmetric(insertion: insertion, removal: removal)
    }
}
struct ContentView: View {
    let questions = [
        Question(id: 1, text: "11111111111"),
        Question(id: 2, text: "222222222222222222222222"),
        Question(id: 3, text: "3333333333333333333"),
        Question(id: 4, text: "444444444444444444444444"),
        Question(id: 5, text: "55555555555555555555"),
        Question(id: 6, text: "6666666666666666666666666")
    ]
    
    @State private var currentQuestionIndex = 0
    @State private var navigationDirection: NavigationDirection = .forward
    
    var body: some View {
        VStack(spacing: 20) {
            Text(questions[currentQuestionIndex].text)
                .id(questions[currentQuestionIndex].id) // Important for transition
                .transition(navigationDirection == .forward ? .slideRight :  .slideLeft)
                .frame(maxWidth: .infinity, maxHeight: .infinity)
            
            HStack {
                Button("Previous") {
                    moveToPreviousQuestion()
                }
                .disabled(currentQuestionIndex == 0)
                
                Spacer()
                
                Button("Next") {
                    moveToNextQuestion()
                }
                .disabled(currentQuestionIndex == questions.count - 1)
            }
        }
        .padding()
        .animation(.easeInOut(duration: 1.0), value: currentQuestionIndex)

    }
    
    private func moveToNextQuestion() {
        if currentQuestionIndex < questions.count - 1 {
            if navigationDirection == .backward {
                navigationDirection = .forward
            }
            Task {
                currentQuestionIndex += 1
            }
        }
    }
    
    private func moveToPreviousQuestion() {
        if currentQuestionIndex > 0 {
            if navigationDirection == .forward {
                navigationDirection = .backward
            }
            Task {
                currentQuestionIndex -= 1
            }
        }
    }
}

enum NavigationDirection {
    case forward, backward
}