social-app/apps/ios/Runner/AppDelegate.swift

import Flutter
import flutter_local_notifications
import UIKit
import UserNotifications

@main
@objc class AppDelegate: FlutterAppDelegate {
  override func application(
    _ application: UIApplication,
    didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
  ) -> Bool {
    FlutterLocalNotificationsPlugin.setPluginRegistrantCallback { registry in
      GeneratedPluginRegistrant.register(with: registry)
    }
    GeneratedPluginRegistrant.register(with: self)
    if #available(iOS 10.0, *) {
      UNUserNotificationCenter.current().delegate = self
    }
    return super.application(application, didFinishLaunchingWithOptions: launchOptions)
  }

  override func userNotificationCenter(
    _ center: UNUserNotificationCenter,
    didReceive response: UNNotificationResponse,
    withCompletionHandler completionHandler: @escaping () -> Void
  ) {
    let userInfo = response.notification.request.content.userInfo
    if let payloadString = userInfo["payload"] as? String {
      UserDefaults.standard.set(payloadString, forKey: "pending_notification_payload")
    }
    completionHandler()
  }
}