What could be the reason for the component not receiving data from the service?

Question

What could be the reason for the component not receiving data from the service?

After attempting to send data from one component to another using a service, I followed the guidance provided in this answer. Unfortunately, the data is not being received by the receiver component. I also explored the solution suggested in this question. Another possibility could be that I am calling the essential "commands" in an incorrect order. It seems there is a specific sequence when working with Observables.

create Observable --> private dataSubject = new Subject();
call Observable --> subscribe();
execute Observable --> next();
dispose --> unsibscribe();

StackBlitz

I am hoping for clarification on whether my understanding of observables is incorrect or if there is a mistake in my implementation. Thank you!

angular typescript rxjs

Answer 1

Answer №1

Your solution had a few mistakes that need to be addressed.

Remember to always unsubscribe from a non-HTTP observable when the component is destroyed.
When pushing a value to a subject, make sure to use next() with the value.
Keep in mind that once the first subscription is created, the name will always be tracked and any new values will appear on the screen after each submit.
(Optional for Cleaner Code), if a function has side effects, it should not return a value (keep queries separate from commands).

I've created a working example based on your code in StackBlitz. You can view it here.

Answer 2

Your solution had a few mistakes that need to be addressed.

Remember to always unsubscribe from a non-HTTP observable when the component is destroyed.
When pushing a value to a subject, make sure to use next() with the value.
Keep in mind that once the first subscription is created, the name will always be tracked and any new values will appear on the screen after each submit.
(Optional for Cleaner Code), if a function has side effects, it should not return a value (keep queries separate from commands).

I've created a working example based on your code in StackBlitz. You can view it here.

Answer 3

Answer №2

Upon reviewing your stackblitz example, it seems that the issue lies in the third part of the question you provided.

3. execute Observable --> next();

You were not properly executing your observable as all you needed to do was pass a value to trigger its execution.

In your service (as shown in the stackblitz code example), you have the following:

sendName(name) {
  this.nameSubject.next(); // executing empty observable
  return name; // unnecessary if value is set in observable
}

Instead, you should be doing the following:

sendName(name) {
  // Pass the name to the observable to trigger its execution rather than returning it
  this.nameSubject.next(name); 
}

Update this in your stackblitz example and it should now work correctly.

Answer 4

Upon reviewing your stackblitz example, it seems that the issue lies in the third part of the question you provided.

3. execute Observable --> next();

You were not properly executing your observable as all you needed to do was pass a value to trigger its execution.

In your service (as shown in the stackblitz code example), you have the following:

sendName(name) {
  this.nameSubject.next(); // executing empty observable
  return name; // unnecessary if value is set in observable
}

Instead, you should be doing the following:

sendName(name) {
  // Pass the name to the observable to trigger its execution rather than returning it
  this.nameSubject.next(name); 
}

Update this in your stackblitz example and it should now work correctly.

What could be the reason for the component not receiving data from the service?

Answer №1

Answer №2

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