Data recovery from sqlite not working

Question

I would like retrieve my articles after my insert in sqlite, but my variable that is supposed to retrieve them is null.

It's the continuation of this post : Function that does not execute

I have a sqliteservice.ts which allows you to create the database and tables, then insert and retrieve the data. The data is inserted but I can not retrieve it in a variable. I call my functions in the constructor of my page.

My service that inserts the data and calls the function to retrieve them :

      public saveAllArticles(article) {

    let insertions: Array<Promise<any>> = [];
    for (let data in article) {
      insertions.push(this.db.executeSql("INSERT INTO `all_articles` (id, titre) VALUES (" +
        article[data].article_id + ',"' +
        article[data].article_titre + "\")", {}))
      Promise.all(insertions).then(() => {
        console.log("All records have been inserted");
        this.allArticles = this.retrieveAllArticles();
      }).catch(e => {
        console.log("Erreur :" + JSON.stringify(e))
      });
    }
  }

When I do a console.log(insertions); before the loop, there is not result in my console, in the loop there is this error :

Uncaught (in promise) TypeError: Cannot read property 'push' of undefined

And this.allArticles is null.

The function to retrieve my articles, this function is not called because the console.log('Retrieve'); is not displayed :

    public retrieveAllArticles() {

    console.log("Retrieve");
    this.allArticles = [];
    this.db.executeSql('SELECT id FROM `all_articles`', {})
      .then((data) => {

      if(data == null) {
        console.log('null');
        return;
      }

      if(data.rows) {
        if(data.rows.length > 0) {
          for(let i = 0; i < data.rows.length; i++) {
            this.allArticles.push(data.rows.item(i).article_id);
          }
        }
      }

        return this.allArticles;
    });
  }

The constructor of my page :

  allArticles: any;
  observable$;

  constructor(public navCtrl: NavController,
              public modalCtrl: ModalController,
              protected articlesService: ArticlesService,
              protected sqliteService: SqliteService,
              private network: Network,
              public toastCtrl: ToastController,
              public platform: Platform)
  {
    this.observable$ = this.articlesService.getAllArticles();

    if (this.platform.is('cordova')) {
      sqliteService.createDatabaseFile();

      this.articlesService.getAllArticles().subscribe(article => {
        this.allArticles = article;
        this.sqliteService.saveAllArticles(this.allArticles);
      });

      this.allArticles = this.sqliteService.allArticles;
    }
  }

where are you calling retrieveAllArticles? and what is `this.allArticles = this.sqliteService.allArticles;` ? — Suraj Rao, Dec 19 '17 at 09:48
I calling retrieveAllArticles() in saveAllArticles() . No it's this.allArticles = this.retrieveAllArticles(); — Valentin Harrang, Dec 19 '17 at 09:55
can you please set the correct code in the question? you also have `this.allArticles = this.sqliteService.allArticles;` in your constructor.. — Suraj Rao, Dec 19 '17 at 09:56
Because I want to store the result of my function in the variable allArticles of my service and set the variable allArticles (it's the same name, but not the same variable, this can be confusing) of my page — Valentin Harrang, Dec 19 '17 at 10:05
well subscribe is async.. so dont think it will do what you intend — Suraj Rao, Dec 19 '17 at 10:07

HMR · Answer 1 · 2017-12-19T10:27:14.307

0

Something wrong with saveAllArticles, it should probably look like this:

public saveAllArticles(article) {
  return Promise.all(//return something so you know when saveAllArticles is done
    //assuming article is an array if it's itterable you may try Array.from(article)
    article.map(
      data=>
        this.db.executeSql(
          "INSERT INTO `all_articles` (id, titre) VALUES (" +
            article[data].article_id + ',"' +
            article[data].article_titre + "\")"
          ,{}
        )
    )
  )
  .then(() => {
    console.log("All records have been inserted");
    this.allArticles = this.retrieveAllArticles();
  }).catch(e => {
    console.log("Erreur :" + JSON.stringify(e))
  });
}

retrieveAllArticles returns undefined, not sure if that is what you wanted. You may want that function to return something.

edited Dec 19 '17 at 10:27

answered Dec 19 '17 at 10:11

HMR

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Yes, I would simply like to retrieve my articles in a variable to exploit it in the constructor of my page – Valentin Harrang Dec 19 '17 at 10:29
No idea ? it's been 4 days that I block on this problem :/ – Valentin Harrang Dec 19 '17 at 10:45
@ElGecko_76 I think you have to do some investigation on how JavaScript event queue works. Then you'd know why a function you write would return a promise and what that promise is. I tried to explain this [here](https://stackoverflow.com/a/47678417/1641941). – HMR Dec 19 '17 at 13:59
I especially would like help to find a solution to my problem, it does not matter if I do not use a promise, as long as it works :/ – Valentin Harrang Dec 19 '17 at 16:44

Data recovery from sqlite not working

1 Answers1