Handle Promise in Obversable for Angular HTTP Interceptor failes

Handle Promise in Observable for Angular HTTP Interceptor Fails

When working with Angular HTTP interceptors, you may come across a situation where you need to handle promises within an observable. This can be a bit tricky as promises and observables have different behaviors and cannot be directly combined. In this blog post, we will explore different solutions to handle promises within an observable in the context of an Angular HTTP interceptor.

Solution 1: Convert Promise to Observable

The first solution is to convert the promise into an observable using the from operator from the rxjs library. This allows us to work with the promise as if it were an observable.

import { from } from 'rxjs';

// Convert promise to observable
const observable = from(promise);

observable.subscribe(
  // Handle successful response
  (response) => {
    console.log('Response:', response);
  },
  // Handle error
  (error) => {
    console.error('Error:', error);
  }
);

Solution 2: Use the mergeMap Operator

An alternative solution is to use the mergeMap operator from the rxjs/operators library. This operator allows us to merge the promise into the observable stream.

import { mergeMap } from 'rxjs/operators';

observable.pipe(
  // Merge promise into observable stream
  mergeMap((response) => promise)
).subscribe(
  // Handle successful response
  (response) => {
    console.log('Response:', response);
  },
  // Handle error
  (error) => {
    console.error('Error:', error);
  }
);

Solution 3: Use the from Operator with toPromise

If you prefer working with promises instead of observables, you can use the from operator with the toPromise method to convert the observable into a promise.

import { from } from 'rxjs';

// Convert observable to promise
const promise = from(observable).toPromise();

promise.then(
  // Handle successful response
  (response) => {
    console.log('Response:', response);
  },
  // Handle error
  (error) => {
    console.error('Error:', error);
  }
);

These are three different solutions to handle promises within an observable in the context of an Angular HTTP interceptor. Choose the solution that best fits your requirements and coding style.