从 sqlite 恢复数据不起作用

Question

我想在我插入到 sqlite 之后检索我的文章，但是我应该检索它们的变量是 null。

这是这篇文章的延续：Function that does not execute

我有一个 sqliteservice.ts，它允许您创建数据库和表，然后插入和检索数据。数据已插入，但我无法在变量中检索它。我在页面的构造函数中调用我的函数。

我的服务插入数据并调用函数来检索它们：

      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))
      });
    }
  }

当我做一个 console.log(insertions);在循环之前，我的控制台中没有结果，在循环中有这个错误：

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

而 this.allArticles 为空。

检索我的文章的函数，这个函数没有被调用，因为console.log('Retrieve');不显示：

    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;
    });
  }

我的页面的构造函数：

  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;
    }
  }

Answer 1

saveAllArticles 出了点问题，应该是这样的：

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 返回未定义，不确定这是否是您想要的。您可能希望该函数返回一些内容。