Unable to retrieve HTTP call response during debugging, although it is visible in the browser

Question

Unable to retrieve HTTP call response during debugging, although it is visible in the browser

When I send an HTTP request to create a record, I am able to see the added record id in the Network section of browsers like Chrome and Firefox. However, when I try to debug the code and retrieve the same id value, I encounter difficulties. I have tried using promises and various other methods, but the issue persists on my PC only. Despite closing antivirus apps, clearing browser history, restarting both the PC and the application, the problem still remains unresolved.

this.myservice.create(<Employee>{ name: data.name, surname: data.surname })
  .pipe(
    tap((result) => {
      // --> Expecting to receive result as id value from the 
      // Network tab of the Google Developer Tools
...

It's worth noting that my service returns an observable without any issues. The problem likely lies within the browser or PC settings, such as firewall configurations.

javascript angular typescript http rxjs

Answer 1

Answer №1

The behavior can vary based on how this.myservice.create is implemented. If it's done eagerly instead of lazily, your http request will be triggered before you subscribe, resulting in the http response being available in the network inspector beforehand. However, the response will only be emitted in the tap() once you actually subscribe() to your Observable, activating the entire stream.

For a 'lazy' implementation example:

create() {
  return Observable.Create((obs) => {
    fetch('http://example.com/movies.json')
      .then(response => {
        obs.onNext(response.json()); 
        obs.onCompleted();
      });
  });
}

This setup will trigger the fetch call only when the observable gets subscribed to.

On the other hand, for an eager implementation example:

create(){
  const obs = new Rx.Subject();
  fetch('http://example.com/movies.json')
    .then(response => {
      obs.next(response.json());
      obs.complete();
    });
  return obs;
}

In this case, the fetch operation starts even if the observable hasn't been subscribed to yet. This could potentially cause a race condition where the value is pushed before subscription.

Having 'eager' observables can often lead to confusion and should generally be avoided as it may not be clear unless there is extensive understanding and documentation of system behavior.

Answer 2

The behavior can vary based on how this.myservice.create is implemented. If it's done eagerly instead of lazily, your http request will be triggered before you subscribe, resulting in the http response being available in the network inspector beforehand. However, the response will only be emitted in the tap() once you actually subscribe() to your Observable, activating the entire stream.

For a 'lazy' implementation example:

create() {
  return Observable.Create((obs) => {
    fetch('http://example.com/movies.json')
      .then(response => {
        obs.onNext(response.json()); 
        obs.onCompleted();
      });
  });
}

This setup will trigger the fetch call only when the observable gets subscribed to.

On the other hand, for an eager implementation example:

create(){
  const obs = new Rx.Subject();
  fetch('http://example.com/movies.json')
    .then(response => {
      obs.next(response.json());
      obs.complete();
    });
  return obs;
}

In this case, the fetch operation starts even if the observable hasn't been subscribed to yet. This could potentially cause a race condition where the value is pushed before subscription.

Having 'eager' observables can often lead to confusion and should generally be avoided as it may not be clear unless there is extensive understanding and documentation of system behavior.

Unable to retrieve HTTP call response during debugging, although it is visible in the browser

Answer №1

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