Could not generate downloadurl

Ionic Framework ionic-v3
1

I’m using this to try to get url into my real time database at firebase, but I only could store is time, path and content type, no url. The error is the 0 is undefined. Need help here, urgent. Thanks in advanced
This is my data.ts code.

import { Injectable } from '@angular/core';
import { AngularFireDatabase } from 'angularfire2/database';
import firebase from 'firebase/app';
import { AngularFireStorage, AngularFireUploadTask } from 'angularfire2/storage';
import 'rxjs/Rx'
 
@Injectable()
export class DataProvider {
 
  constructor(private db: AngularFireDatabase, private afStorage: AngularFireStorage) {
    
   }
 
  getFiles() {
    let ref = this.db.list('files');
 
    return ref.snapshotChanges().map(changes => {
      return changes.map(c => ({ key: c.payload.key, ...c.payload.val() }));
    });
  }
 
  uploadToStorage(information): AngularFireUploadTask {
    let newName = `${new Date().getTime()}.txt`;
 
    return this.afStorage.ref(`files/${newName}`).putString(information);
  }
 
  storeInfoToDatabase(metainfo) {
    let toSave = {
      created: metainfo.timeCreated,
      url: metainfo.downloadURL[0],
      fullPath: metainfo.fullPath,
      contentType: metainfo.contentType
    }
    return this.db.list('files').push(toSave);
  }
 
 
  deleteFile(file) {
    let key = file.key;
    let storagePath = file.fullPath;
 
    let ref = this.db.list('files');
 
    ref.remove(key);
    return this.afStorage.ref(storagePath).delete();
  }
}