Ionic4 toast.present（）在Ionic 4中失败

有人能帮我把这个翻译成爱奥尼亚-4吗

  async addTransaction() {
this.ref = this.db.list('transactions', ref => ref.orderByChild('month'));
this.ref.push(this.transaction).then(() => {
  this.transaction = {
    value: 0,
    expense: false,
    month: 0,
  };

  let toast = this.toastCtrl.create({
    message: 'New transaction has been added!',
    duration: 3000
  });
  toast.present();
});
}

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请先查阅文件

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你看过医生了吗？

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

@Component({
  selector: 'toast-example',
  templateUrl: 'toast-example.html',
  styleUrls: ['./toast-example.css'],
})
export class ToastExample {

  constructor(public toastController: ToastController) {}

  async presentToast() {
    const toast = await this.toastController.create({
      message: 'Your settings have been saved.',
      duration: 2000
    });
    toast.present();
  }

  async presentToastWithOptions() {
    const toast = await this.toastController.create({
      header: 'Toast header',
      message: 'Click to Close',
      position: 'top',
      buttons: [
        {
          side: 'start',
          icon: 'star',
          text: 'Favorite',
          handler: () => {
            console.log('Favorite clicked');
          }
        }, {
          text: 'Done',
          role: 'cancel',
          handler: () => {
            console.log('Cancel clicked');
          }
        }
      ]
    });
    toast.present();
  }

}