fire action only after notification appears (swift3)

My code uses a datePicker, that when the datePicker is changed and matches the current date of the user device. It fires a notification. However the AVSpeechUtterance I am using fires as soon as the datePickers time is changed not when the notification appears. I would like the AVSpeechUtterance and notification to be be fired at the same time.

import UIKit
import  AVFoundation
import UserNotifications

class ViewController: UIViewController {
@IBOutlet var datePicker: UIDatePicker!

@IBAction func datePicker(_ sender: Any) {
    let c = UNMutableNotificationContent()
    c.title = "Lets Roll"
    c.subtitle  = "s"
    c.body = "d"

    let begin = AVSpeechUtterance(string: " Hello ")

    let synthesizer = AVSpeechSynthesizer()

    begin.voice = AVSpeechSynthesisVoice(language: "en-US")
    begin.rate = 0.08

    synthesizer.speak(begin)

    let triggerDate = Calendar.current.dateComponents([.year, .month, .day, .hour, .minute], from: datePicker.date )
    let t = UNCalendarNotificationTrigger(dateMatching: triggerDate, repeats: false)
    let r = UNNotificationRequest(identifier: "any", content: c, trigger: t)

    UNUserNotificationCenter.current().add(r, withCompletionHandler: nil)
}}

APP DELEAGATE

  import AVFoundation
   import UIKit
   import UserNotifications

 enum NotificationName: String {
case mySpeechNotification
 }


   @UIApplicationMain
   class AppDelegate: UIResponder, UIApplicationDelegate, UNUserNotificationCenterDelegate {

var window: UIWindow?

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
    if #available(iOS 10.0, *) {
        let center = UNUserNotificationCenter.current()
        center.delegate = self
        center.requestAuthorization(options: [.alert, .badge, .sound]) { (granted, error) in
            if error != nil {
                print("Ops, error trying to get authorization")
            } else {
                if !granted {
                    print("Dude, let me use notifications!")
                }
            }
        }
    }
    return true
}

 func userNotificationCenter(_ center: UNUserNotificationCenter, willPresent notification: UNNotification, withCompletionHandler completionHandler: @escaping (UNNotificationPresentationOptions) -> Void)     {
     print("Oh, will present a notification, let's see the identifier: \(notification.request.identifier)")
    if (notification.request.identifier == NotificationName.mySpeechNotification.rawValue) {
        print("Speaking...")
               } else {
        print("Nothing to say...")
    }

    completionHandler(.alert)
    let begin = AVSpeechUtterance(string: " Hello ")
    begin.voice = AVSpeechSynthesisVoice(language: "en-US")
    begin.rate = 0.08

    let synthesizer = AVSpeechSynthesizer()
    synthesizer.speak(begin)


}

  }