Exntension to `UNNotification` for "snoozing" a notification.

UNNotification+Reschdule.swift

//
//  UNNotification+Reschedule.swift
//  Meal Plan
//
//  Created by Simon Ljungberg on 17/11/16.
//  License: MIT
//

import UIKit
import UserNotifications

extension UNNotification {
    func snoozeNotification(for hours: Int, minutes: Int) {
        let content = self.request.content
        let identifier = self.request.identifier
        guard let oldTrigger = self.request.trigger as? UNCalendarNotificationTrigger else {
            fatalError("Cannot reschedule notification without calendar trigger.")
        }

        var components = oldTrigger.dateComponents
        components.hour = (components.hour ?? 0) + hours
        components.minute = (components.minute ?? 0) + minutes

        let trigger = UNCalendarNotificationTrigger(dateMatching: components, repeats: false)
        let request = UNNotificationRequest(identifier: identifier, content: content, trigger: trigger)
        UNUserNotificationCenter.current().add(request) { error in
            if let error = error {
                print("Reschduling failed", error.localizedDescription)
            }
        }
    }
}