侦听事件时推送数组

Question

我正在使用Ionic，我想在事件发生时推送一个对象的数组。

我有这样一个

    export  class PublicationService {

    constructor(
        private storage: Storage
    ){}

    private addPublicationSubject = new BehaviorSubject<PublicationModel>(new PublicationModel());
    data = this.addPublicationSubject.asObservable();

    publishData(data: PublicationModel) {
        this.addPublicationSubject.next(data);
    }
   }

在这里，发出事件

    savePublication() {
    this.newPublication.id_pub = 1;
    this.newPublication.textPub = this.f.text.value;
    this.newPublication.user_sender = 'Juance';
    this.newPublication.datetime = "asd";
    this.pubService.publishData(this.newPublication);
  }

在我的主页上，该事件是监听（在ngOnInit中）。

// Variable defined in the component
publications: PublicationModel[] = [];

//ngOnInit
this.pubService.data.subscribe((data) => {
      if (data != null) {
        console.log(data);

        this.publications.push(data);
      }
});

现在我的问题是：当我试图将数据推送到数组中时，它告诉我它不能读取null的属性（this.publications）。

当进入事件的订阅时，它不接受组件中定义的变量。有什么办法吗？

EDIT:

我的组件HomePage

    @Component({
  selector: 'app-home',
  templateUrl: 'home.page.html',
  styleUrls: ['home.page.scss']
})
export class HomePage implements OnInit {

  viewAddPublication: boolean;
  publications: PublicationModel[] = [];
  countLikePub:   number;
  addPublication: any;

  constructor(
    private storage: Storage,
    private navCtrl: NavController,
    private pubService: PublicationService) {
      this.publications = new Array<PublicationModel>();
  }

  ngOnInit() {
    this.publications = [];

    this.pubService.data.subscribe((data) => {
      if (data != null) {
        console.log(data);

        this.setData(data);
      }
    }
    );
    this.viewAddPublication = false;
    this.countLikePub = 0;

    this.storage.get('publications').then((val) => {
      this.publications = val;
    });

  }

  setData(data) {
    this.publications.push(data);
  }

  goToAddPub() {
    this.navCtrl.navigateForward('/add-publication', {
      animated: true,
      animationDirection: "forward",

    });
  }

  public likedPost(event) {
    console.log();
    let like = (document.getElementById(event.target.id) as HTMLElement);
    like.style.color = '#0277bd';
    this.countLikePub++;
  }

调试模式

我需要一个实时推送数组的方法，这是我能想到的唯一方法，另一个方法是使用Socket.io。

Answer 1

我想也许你将出版物设置为 null 因为这个功能。

this.storage.get('publications').then((val) => {
  this.publications = val;
});

你可以把它改一下 确保出版物仍然是一个数组。

this.storage.get('publications').then((val) => {
   this.publications = val || [];
});

我补充道 this.publications = val || []; 这是在创建一个空数组，如果 val 未定义