Scheduler

HomeViewController.swift

import UIKit

class HomeViewController: UIViewController {
  private let uniqueKey: String = "hkjladjgaldkjakjl"
  ...
  
  override func viewWillAppear(_ animated: Bool) {
    super.viewDidLoad()
    Scheduler.shared.monitors.updateValue( self, forKey: uniqueKey)
  }
  
  override func viewWillDisappear(_ animated: Bool) {
    super.viewDidLoad()
    Scheduler.shared.monitors.removeValue(forKey: String)
  }
}

extension HomeViewController: ScheduleMonitor {
  func update(dateOfHHmmFormat: String) {
    ...
  }
}

ScheduleMonitor.swift

protocol ScheduleMonitor {
  func update(dateOfHHmmFormat: String)
}

Scheduler.swift

class Scheduler {
  var monitors: [String: ScheduleMonitor]
  private let formatter: DateFormatter = {
    let _HHmmFormatter = DateFormatter()
    formatter.dateformat = "HH:mm"
    return formatter
  }()
  
  static let shared = Scheduler()
  
  init(monitors: [String:ScheduleMonitor] = [:]) {
    self.monitors = monitors
  }
  
  @objc private func updateCurrentTime() {
    let date = Date()
    let currentTimeText = _HHmmFormatter.string(date: date)
    self.monitors.foreach { monitor in
      monitor.update(dateOfHHmmFormat: currentTimeText)
    }
  }
}