Using setMessage method in alert component

alert-demo.ts

import { Component } from '@angular/core';
import { AlertController } from '@ionic/angular';

@Component({
  selector: 'app-home',
  templateUrl: 'home.page.html',
  styleUrls: ['home.page.scss']
})
export class HomePage {
  alert: any;
  constructor(public alertController: AlertController) {}

  async presentAlert() {
    this.alert = await this.alertController.create({
      header: 'Alert',
      subHeader: 'Subtitle',
      message: 'This is an alert message.',
      buttons: ['OK']
    });
    await this.alert.present();
    this.updateAlertMessage();
  }

  updateAlertMessage() {
    setTimeout(() => {
      // ionic 3
      this.alert.setMessage('This the updated Alert Message');

      // ionic 4
      this.alert.message = 'This the updated Alert Message';
    }, 3000);
  }
}