SpeedometerDataModel.swift

import SwiftUI
import CoreLocation

final class DataModel: NSObject, ObservableObject, CLLocationManagerDelegate {
  static let shared = DataModel()
  private let locationManager = CLLocationManager()
  private var multiplier: Double { return isKPH ? 3.6 : 2.236936 }
  
  private override init() {
    super.init()
    locationManager.start(delegate: self)
  }
  @Published private(set) var speed = Double()

  @Published var isKPH = UserDefaults.standard.bool(forKey: .isKPH) {
    didSet { UserDefaults.standard.set(isKPH, forKey: .isKPH) }
  }
  
  private func updateSpeed(value: Double) {
    speed = .zero
    if value > 1 { speed = value + 0.5 }
  }
  func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
    let speedFromGPS = locationManager.speed(multipliedBy: multiplier)
    updateSpeed(value: speedFromGPS)
  }
}