///// With this it gives me the error.
const posts = data[1].posts;
        posts.map(post => {
          if (post.id === this.id) {
            this.postIWant = post.fileText;
          }
        });

/////////////////////////////////////

////// The old way didnt.
/// OLD way below

this.postsSub = this.postsService
      .getPostUpdateListenerTwo()
      .subscribe((posts: Post[]) => {
        this.posts = posts;
        this.posts.map(post => {
          if (post.id === this.id) {
            this.postIWant = post.fileText;
          }
        });
      });