How to perform async validation using reactive/model-driven forms in Angular 2 - forms

Question

I have an email input and I want to create a validator to check, through an API, if the entered email it's already in the database.
So, I have:
A validator directive
import { Directive, forwardRef } from '#angular/core';
import { Http } from '#angular/http';
import { NG_ASYNC_VALIDATORS, FormControl } from '#angular/forms';
export function validateExistentEmailFactory(http: Http) {
return (c: FormControl) => {
return new Promise((resolve, reject) => {
let observable: any = http.get('/api/check?email=' + c.value).map((response) => {
return response.json().account_exists;
});
observable.subscribe(exist => {
if (exist) {
resolve({ existentEmail: true });
} else {
resolve(null);
}
});
});
};
}
#Directive({
selector: '[validateExistentEmail][ngModel],[validateExistentEmail][formControl]',
providers: [
Http,
{ provide: NG_ASYNC_VALIDATORS, useExisting: forwardRef(() => ExistentEmailValidator), multi: true },
],
})
export class ExistentEmailValidator {
private validator: Function;
constructor(
private http: Http
) {
this.validator = validateExistentEmailFactory(http);
}
public validate(c: FormControl) {
return this.validator(c);
}
}
A component
import { Component } from '#angular/core';
import { FormGroup, FormBuilder, Validators } from '#angular/forms';
import { ExistentEmailValidator } from '../../directives/existent-email-validator';
#Component({
selector: 'user-account',
template: require<string>('./user-account.component.html'),
})
export class UserAccountComponent {
private registrationForm: FormGroup;
private registrationFormBuilder: FormBuilder;
private existentEmailValidator: ExistentEmailValidator;
constructor(
registrationFormBuilder: FormBuilder,
existentEmailValidator: ExistentEmailValidator
) {
this.registrationFormBuilder = registrationFormBuilder;
this.existentEmailValidator = existentEmailValidator;
this.initRegistrationForm();
}
private initRegistrationForm() {
this.registrationForm = this.registrationFormBuilder.group({
email: ['', [this.existentEmailValidator]],
});
}
}
And a template
<form novalidate [formGroup]="registrationForm">
<input type="text" [formControl]="registrationForm.controls.email" name="registration_email" />
</form>
A've made other validator this way (without the async part) and works well. I think te problem it's related with the promise. I'm pretty sure the code inside observable.subscribe it's running fine.
What am I missing?
I'm using angular v2.1

Answer 1

Pretty sure your problem is this line:
...
email: ['', [this.existentEmailValidator]],
...
You're passing your async validator to the synchronous validators array, I think the way it should be is this:
...
email: ['', [], [this.existentEmailValidator]],
...
It would probably be more obvious if you'd use the new FormGroup(...) syntax instead of FormBuilder.