17072020-solution.swift

func requestAuthorization(completion: @escaping (Result<Bool, Error>) -> Void) {
	
	var authorizationOptions: UNAuthorizationOptions = [.badge, .alert, .sound]
	if #available(iOS 12.0, *) {
		authorizationOptions.insert(.criticalAlert)
	}
	
	let notificationCenter = UNUserNotificationCenter.current()
	notificationCenter.requestAuthorization(options: authorizationOptions) { (granted, possibleError) in
		
		guard possibleError == nil else {
			completion(.failure(possibleError!))
			return
		}
		
		completion(.success(granted))
	}
}