Tips for managing errors when using the mergeMap feature in Angular's Typeahead search

Currently working on implementing Typeahead search functionality using API data. When we input valid data, the autosuggestions work correctly. However, if we input invalid data, we receive an error message. The issue arises when trying to input valid data again, as the API does not trigger. In order to address this, I have attempted the following code. Any guidance on how to handle error scenarios for invalid data would be greatly appreciated.

asyncData: string;
dataSource: Observable<any>;

this.dataSource = new Observable((observer) => {
    observer.next(this.asyncData)
}).mergeMap(() => {
    return this.http.get('/api/testAPI',{params: {param1: param1}});
});

Answer №1

It appears that the use of new Observable() may not be necessary in this scenario. The code snippet does not include the usage of the HTTP request. However, it is crucial to implement error handling. One way to handle errors is by using the catchError operator to either convert errors into valid responses or prevent them from being emitted.

import { NEVER } from 'rxjs';
import { catchError } from 'rxjs/operators';

return this.http.get('/api/testAPI',{params: {param1: param1}}).pipe(
  catchError(() => NEVER)
);

The code snippet utilizes the RxJS NEVER constant, which ensures that no emissions will occur. It is important to note that if you intend to handle errors within the subscription, this approach will not emit any errors.

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