Accurately Showing Values of Observable Objects

Hey there, I'm diving deeper into Angular and working on my first project. I am fetching data from my database using a service method:

  getPost(postID: String) {
    this.postDocument = this.db.doc('posts/' + postID)
    return this.postDocument.valueChanges()
  }

I am calling this method inside my component

  ngOnInit() {
    this.currentPost = this.route.paramMap.pipe(
      switchMap((params: ParamMap) => this.fs.getPost(params.get('id')))
    )
  }

Everything is working fine so far, but I am struggling to display the data in my HTML. For instance, I am encountering an issue where it shows that 'title' is null even though it is displaying correctly.

<div>
  post-read-page works!
  <h1 *ngIf="currentPost">{{ (currentPost | async).title }}</h1>
</div>

Thank you in advance!

Exact Error:

ERROR TypeError: Cannot read property 'title' of null

Answer №1

An important consideration is that the variable currentPost may also be null, so it's crucial to properly handle the null case in the template to avoid encountering errors. One approach, as mentioned in a comment, is to utilize the safe navigation operator (?.) to address this issue.

With this approach, your binding would appear as follows:

<div>
  The post-read-page functionality is operational!
  <h1 *ngIf="currentPost">{{ (currentPost | async)?.title }}</h1>
</div>

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