Angular - Scope variable not updating after subscription

Question

Angular - Scope variable not updating after subscription

Having some trouble with a piece of code that subscribes from our service:

Method getVideo()

  getVideo() {
    this.watchService.getVideoByVideoString(this.videoId).subscribe(
      (Response) => {
        this.videoData = Response;
        console.log(Response);
      },
      (err) => console.log(err)
    );
  }

ngOnInit Method

  ngOnInit() {

    this.getVideo();
    console.log(this.videoData);
}

Unfortunately, when I try to access this.videoData, it shows up as undefined. Can someone assist me with this issue?

Thank you.

======

Updated

After running some tests, I found out that I need to manipulate the data within the function itself instead of in the NgOnInit.

The final solution looks like this:

  getVideo() {
    this.watchService.getVideoByVideoString(this.videoId).subscribe(
      (Response) => {
        this.videoData = Response;

        if (this.videoData.title == null) {
          this.titleService.setTitle('InternalVideoChannel');
        } else {
          this.titleService.setTitle('InternalVideoChannel - ' + this.videoData.title);
        }
        if (this.videoData.id == 0) {
          console.log('Video doesnt exist on the database');
          this.router.navigate(['/notFound']);
        }
        console.log(Response);
      },
      (err) => console.log(err)
    );
  }

Thanks!

javascript angular typescript subscribe

Answer 1

Answer №1

Here is the accurate syntax:

 fetchClip() {
this.playbackService.fetchClipByClipString(this.clipId).subscribe(
  (result) => {
      this.clipData = result;
      console.log(result);
      },
  (error) => console.log(error);
);

}

Answer 2

Here is the accurate syntax:

 fetchClip() {
this.playbackService.fetchClipByClipString(this.clipId).subscribe(
  (result) => {
      this.clipData = result;
      console.log(result);
      },
  (error) => console.log(error);
);

}

Answer 3

Answer №2

It seems like a bit more context is needed in this situation. If you have a console log before the subscription and variable assignment, you'll always receive undefined for this.videoData.

If you specifically want to check if the value was assigned to the property this.videoData of your class, the console.log should be placed right alongside the assignment within the subscription.

Keep in mind the potential memory leaks that can occur from not unsubscribing from an observable.

Edit: As you can see, the console.log is outside the scope of the subscription, resulting in undefined due to the asynchronous nature of an observable subscription.

ngOnInit():void {
   console.log(this.videoData) <- this will be undefined
   this.getVideo(); // <- async 
   console.log(this.videoData) <- this will be undefined
}

The only way to retrieve the value is by console.logging inside the subscription hook like so:

getVideo() {
this.watchService.getVideoByVideoString(this.videoId).subscribe(
  (Response) => {
    this.videoData = Response;
    console.log(Response);
    console.log(this.videoData); // your console.log 
  },
  (err) => console.log(err)
);

The observed issue relates to the behavior of an observable, as it operates similarly to a promise. The console.log runs before the actual assignment takes place, necessitating the need to either bind a function to access the stored value or log within the subscription.

Third edit: If you wish to access the value at a specific point in your application, there isn't a direct solution. However, creating a function that you manually call when needed, perhaps using a timeout or click event, could be a suitable approach.

logVideoDataValue():void {
   console.log(this.videoData) 
}

Answer 4

It seems like a bit more context is needed in this situation. If you have a console log before the subscription and variable assignment, you'll always receive undefined for this.videoData.

If you specifically want to check if the value was assigned to the property this.videoData of your class, the console.log should be placed right alongside the assignment within the subscription.

Keep in mind the potential memory leaks that can occur from not unsubscribing from an observable.

Edit: As you can see, the console.log is outside the scope of the subscription, resulting in undefined due to the asynchronous nature of an observable subscription.

ngOnInit():void {
   console.log(this.videoData) <- this will be undefined
   this.getVideo(); // <- async 
   console.log(this.videoData) <- this will be undefined
}

The only way to retrieve the value is by console.logging inside the subscription hook like so:

getVideo() {
this.watchService.getVideoByVideoString(this.videoId).subscribe(
  (Response) => {
    this.videoData = Response;
    console.log(Response);
    console.log(this.videoData); // your console.log 
  },
  (err) => console.log(err)
);

The observed issue relates to the behavior of an observable, as it operates similarly to a promise. The console.log runs before the actual assignment takes place, necessitating the need to either bind a function to access the stored value or log within the subscription.

Third edit: If you wish to access the value at a specific point in your application, there isn't a direct solution. However, creating a function that you manually call when needed, perhaps using a timeout or click event, could be a suitable approach.

logVideoDataValue():void {
   console.log(this.videoData) 
}

Angular - Scope variable not updating after subscription

Answer №1

Answer №2

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