What is the best way to populate an Angular variable in Ionic following a subscription?

Currently, I am in the process of retrieving data from a server and displaying it on an Ionic page. I have successfully fetched the data without any issues and verified it in the console. However, how do I proceed once the server returns the data to me?

The function responsible for loading the article is located within a provider:

public LoadArticle(article_id:any){
    let headers = new Headers();
    let postData:any;
    postData = {
      task: 'GetArticle',
      article_id: article_id
    }

    headers.append('Content-Type', 'application/x-www-form-urlencoded; charset=UTF-8');
    return this.http.post(this.apiUrl, JSON.stringify(postData),{ headers: headers });
  }

To display the article, I call this function on the desired page:

constructor(
    public navCtrl: NavController,
    public controller: WebservicesProvider
  ) {

  }
this.controller.LoadArticle(1).subscribe(
      data => {
        let retorno: any;
        retorno = data;
        console.log(JSON.parse(retorno._body));
        // this.navCtrl.setRoot(AbasPage);        
        // this.article_array = retorno._body.dados;

        this.articlearray.id = retorno._body.dados.id;

        this.articleLoaded = true;
      },
      error => {
        console.log(error)
        this.controller.endLoading();
      },
      () => {
        this.controller.endLoading();
      }
    );

When attempting to reference {{articlearray.id}} in the HTML file of the page, I encounter the following error:

Cannot read property 'id' of undefined

I'm puzzled as to what could be causing this issue. Where might I be going wrong in my implementation?

Answer №1

I encountered an error when trying to include {{articlearray.id}} in the page's HTML file.

To avoid this error, you can utilize the safe navigation operator:

{{articlearray?.id}}

By using this approach, the error will be prevented and the data will be displayed once it is fetched.

Initially, when the template is shown, the data has not yet been retrieved which results in the error message. However, as the data is later fetched, Angular's change detection system will update the display to show the retrieved information.

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