【SwiftUI & Kronos】NTP から時刻を取得し端末の設定によらず正しい Date を得る

ContentView.swift

//
//  ContentView.swift
//  Shared
//
//  Created by treastrain on 2021/03/03.
//

import SwiftUI
import Kronos

@main
struct testApp: App {
    var body: some Scene {
        WindowGroup {
            ContentView().environmentObject(ContentViewHolder())
        }
    }
}

class ContentViewHolder: ObservableObject {
    private var timer: Timer!
    private let formatter = DateFormatter()
    @Published var timeStr = "時間を表示します…"
    
    init() {
        Clock.sync(from: "ntp.nict.jp")
        
        self.formatter.locale = Locale(identifier: "ja_JP")
        self.formatter.dateStyle = .medium
        self.formatter.timeStyle = .medium
        
        self.timer?.invalidate()
        self.timer = Timer.scheduledTimer(timeInterval: 1/60, target: self, selector: #selector(self.tick), userInfo: nil, repeats: true)
    }
    
    @objc
    func tick() {
        if let date = Clock.now {
            self.timeStr = self.formatter.string(from: date)
        }
    }
}

struct ContentView: View {
    @EnvironmentObject var holder: ContentViewHolder
    
    var body: some View {
        Text(holder.timeStr)
            .font(Font.body.monospacedDigit())
            .padding()
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}