Function that does not execute

Question

I have a function to insert my articles and I call this function in my page, there is no error, but the next function retrievedAllArticles() is not executed.

    public saveAllArticles(article) {
    for(let data in article) {
      this.db.executeSql("INSERT INTO `all_articles` (id, titre, introduction, image, redacteur_nom, redacteur_twitter, date_publication, contenu_part1, tweet, image2, contenu_part2, tweet2, image3, contenu_part3, tweet3, image4, contenu_part4, tweet4, image5, contenu_part5, tweet5, image6, contenu_part6, tweet6, image7, contenu_part7, tweet7, image8, contenu_part8, tweet8, image9, contenu_part9, tweet9, image10, contenu_part10, tweet10) VALUES (" +
        article[data].article_id + ',"' +
        article[data].article_titre + "\")", {})
        .then(() => {
          console.log("Inséré");
        }).catch(e =>
        console.log("Erreur :" + JSON.stringify(e))
      );
    }
  }


  public retrieveAllArticles() {

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

      console.log(data);

      if(data == 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 console.log("Retrieve"); is not displayed, but the console.log('Inséré'); is displayed.

The constructor of my page :

    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.retrieveAllArticles();
    }
  }

After suggestions :

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.retrieveAllArticles();
        console.log("articles");
        console.log(this.allArticles);
      });

    }
  }

    public saveAllArticles(article) {

    let insertions: Array<Promise<any>> = [];
    console.log("insertions", insertions);
    for (let data in article) {
      insertions.push(this.db.executeSql("INSERT INTO `all_articles` (id, titre, introduction, image, redacteur_nom, redacteur_twitter, date_publication, contenu_part1, tweet, image2, contenu_part2, tweet2, image3, contenu_part3, tweet3, image4, contenu_part4, tweet4, image5, contenu_part5, tweet5, image6, contenu_part6, tweet6, image7, contenu_part7, tweet7, image8, contenu_part8, tweet8, image9, contenu_part9, tweet9, image10, contenu_part10, tweet10) 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))
      });
    }
  }

Can you help me please ?

Thank you in advance

You should move `this.allArticles = this.sqliteService.retrieveAllArticles();` inside of the `subscribe` callback, after `saveAllArticles`. In your current code, `retrieveAllArticles` is probably executed before the callback. — ConnorsFan, Dec 18 '17 at 19:54
Thank you ! : D, it's normal if the console.log ("Retrieve"); is displayed before "Inserted" in my console while the insertion is done before the retrieval of articles? — Valentin Harrang, Dec 18 '17 at 19:58
If these commands are asynchronous (as they probably are), putting `retrieveAllArticles` at the end of the callback ensures that it is executed after `saveAllArticles`. — ConnorsFan, Dec 18 '17 at 20:01
So, it's normal ? Because when I console.log(this.allArticles); in the constructor of my page, the variable is empty — Valentin Harrang, Dec 18 '17 at 20:05
I am not sure what the order of execution would be. Event with my first suggestion, the order is not well determined, actually. To be really sure, you should retrieve the data after `saveAllArticles` completes. — ConnorsFan, Dec 18 '17 at 20:16
Sorry for the confusion. My first suggestion was not accurate. As your code is now, you call `retrieve` after calling `save`, but not after `save` has completed. Since these calls are asynchronous, `save` completes when the all the promises have been completed (when the last item has been inserted and the promise returns with `then` or `catch`). — ConnorsFan, Dec 18 '17 at 20:28
So you could run `retrieveAllArticles` just after `console.log("Inséré")`, but only for the last inserted element. Maybe someone else can suggest an elegant way to do that... — ConnorsFan, Dec 18 '17 at 20:30
Yes. :-) But `retrieve` should be executed only after the last one has been inserted. You can try the (untested) code in my answer. — ConnorsFan, Dec 18 '17 at 21:03

ConnorsFan · Answer 1 · 2017-12-19T01:29:14.377

0

To make sure that you retrieve the data after all the saving operations have completed, you can try this:

public saveAllArticles(article) {
  // Make an array of all promises
  let insertions: Array<Promise<any>> = [];
  for (let data of article) {
    insertions.push(this.db.executeSql("INSERT INTO ...", {}));
  }
  // Execute all promises and retrieve all articles afterwards
  Promise.all(insertions).then(() => {
      console.log("All records have been inserted");
      this.allArticles = this.sqliteService.retrieveAllArticles();
    }).catch(e => {
      console.log("Error: " + JSON.stringify(e))
    });
}

The method for grouping of promises is taken from this answer by Günter Zöchbauer.

edited Dec 19 '17 at 01:29

answered Dec 18 '17 at 21:01

ConnorsFan

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let insertions is underline in red : the undefined [] is not assignable to type Promise. Property then is missing in type undefined[] . I edited my post – Valentin Harrang Dec 18 '17 at 21:13
I had forgotten to define `insertions` as an array. I updated the answer. – ConnorsFan Dec 18 '17 at 21:15
[22:17:58] console.log: Retrieve [22:17:58] console.log: All records have been inserted [22:17:58] console.log: Retrieve [22:17:58] console.log: All records have been inserted [22:17:58] console.log: Retrieve ...... – Valentin Harrang Dec 18 '17 at 21:18
Uncaught (in promise) TypeError: Cannot read property 'push' of undefined – Valentin Harrang Dec 18 '17 at 21:26
Is `insertions` undefined? Can you put `console.log("insertions", insertions);` before the `for` loop and see if it is OK? – ConnorsFan Dec 18 '17 at 21:39
Yes insertions is undefined : [22:41:49] console.log: insertions – Valentin Harrang Dec 18 '17 at 21:43
And the previous line is exactly `let insertions: Array> = [];`? – ConnorsFan Dec 18 '17 at 21:44
I don't understand that. Can you put the new code of `saveAllArticles` in your question? – ConnorsFan Dec 18 '17 at 21:47
this.allArticles is null when I console.log(this.allArticles); after this.allArticles = this.retrieveAllArticles(); – Valentin Harrang Dec 18 '17 at 22:16
At the start of the function, you can check if `article` is OK (with `console.dir(article)`. Also, if `article` is an array, you may need to use `of` instead of `in` (like `for (let data of article)`). – ConnorsFan Dec 18 '17 at 22:26
[23:29:25] console.dir: [object Object],[object Object],[object Object],[object Object],[object Object],.... – Valentin Harrang Dec 18 '17 at 22:31
If I use of instead of in, when I console.log(data), the result is [23:49:24] console.log: [object Object] – Valentin Harrang Dec 18 '17 at 22:52

Function that does not execute

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