Angular 16 - implementing Handling Reactive Forms and Custom Validators for Async Data Fetching
I'm currently working with Angular 16 and working with an scenario while trying to implement reactive forms with custom async validators that fetch data from an API. I created a form with a control that needs to check if an email already exists in the database. I'm using a custom validator to make an HTTP request. However, I'm running into the question where the validation is not behaving as expected, sometimes returning `null` when I believe it should return an behavior object. Here is a simplified version of my form setup: ```typescript import { Component } from '@angular/core'; import { FormBuilder, FormGroup, Validators } from '@angular/forms'; import { HttpClient } from '@angular/common/http'; import { Observable, of } from 'rxjs'; import { map, catchError } from 'rxjs/operators'; @Component({ selector: 'app-email-form', templateUrl: './email-form.component.html', }) export class EmailFormComponent { emailForm: FormGroup; constructor(private fb: FormBuilder, private http: HttpClient) { this.emailForm = this.fb.group({ email: ['', [Validators.required, Validators.email], [this.emailAsyncValidator.bind(this)]], }); } emailAsyncValidator(control: AbstractControl): Observable<ValidationErrors | null> { if (!control.value) return of(null); return this.http.get(`/api/check-email?email=${control.value}`).pipe( map((response: any) => { return response.exists ? { emailExists: true } : null; }), catchError(() => of(null)) ); } } ``` In my API, I return an object like `{ exists: true }` if the email is taken. However, sometimes my validator returns `null` even when I input an email that is definitely in the database. I’ve also checked my API and it responds correctly with the expected data. I’ve verified that the control value is being passed correctly, and I can see the network request firing in the developer tools. Yet, intermittently it still shows that the email is valid when it should not be. What could be causing this scenario? Any tips on how to stabilize the async validation process? I also tried adding a debounce time to the validator, but it didn't seem to improve the situation. Any help would be greatly appreciated!