import SwiftUI

struct ContentView: View {
    
    private let letters: [String] = ["A", "B", "C"]
    private let numbers: [Int] = [
        4, 5, 21,     // A, B, C
        23, 27, 36,   // A, B, C
        37, 52, 59    // A, B, C
    ]
    
    @State private var randomNumber: Int = 0
    @State private var rotation: CGFloat = 0.0
    @State private var started: Bool = false
    
    var body: some View {
        VStack {
            ZStack {
                ZStack {
                    Circle()
                        .foregroundColor(.blue)
                    ForEach(letters.indices) { i in
                        Text(letters[i])
                            .foregroundColor(.white)
                            .offset(x: 0, y: -110)
                            .rotationEffect(.degrees(Double(i * (360 / letters.count))))
                    }
                }
                .frame(width: 250, height: 250, alignment: .center)
                .rotationEffect(.degrees(rotation))
                
                VStack {
                    Text("Rotation: \(rotation, specifier: "%.2f")")
                    Text("Number: \(randomNumber)")
                    Text("Closest: \(closest(to: randomNumber))")
                }
            }
            
            Spacer()
                .frame(height: 50)
            Button(started ? "Stop" : "Start", action: started ? stop : start)
                .buttonStyle(.borderedProminent)
                .tint(started ? .red : .blue)
        }
    }
    
    private func start() {
        started = true
        loop()
    }
    
    private func stop() {
        started = false
    }
    
    private func loop() {
        if !started { return }
        
        randomNumber = .random(in: numbers.min()!...numbers.max()!)
        withAnimation { 
            rotation = CGFloat(0)
        }
        
        DispatchQueue.main.asyncAfter(deadline: .now()   1, execute: loop)
    }
    
    private func closest(to x: Int) -> Int {
        return numbers.enumerated().min(by: { abs($0.1 - x) < abs($1.1 - x)})!.element
    }
}

Hello, I want to rotate the zstack according to randomNumber value to match the letter number in array for example if randomNumber = 30 closest number = 27 which is labeled B in the circle I want to rotate the zstack so the letter B point to north but a little offset because the number is 30 not 27 exactly

The code above is example the calculation happens in loop function inside withAnimation brackets

Thank you

CodePudding user response：

Here is a proposal for your loop, so the rotation picks the closest number in the array:

            randomNumber = .random(in: numbers.min()!...numbers.max()!)
            let differences = numbers.compactMap { abs($0 - randomNumber) }.sorted { $0 < $1 }
            let closest = randomNumber - (differences.first ?? 0)
                
            withAnimation {
            if numbers.contains(closest) {
                    rotation = closest
                } else {
                    rotation = randomNumber   (differences.first ?? 0)
                }
            }

Just remember to use the proper types (Int, CGFloat…).