.setAsyncValidator

The .setAsyncValidator rule is one of the special async rules that become available when you extend from AsyncValidator as opposed to just Validator.

This rule works exactly the same as the .setValidator rule, except that you must pass an instance of AsyncValidator as opposed to an instance of Validator.

As with the .setValidator rule, the async validator to use is specified by way of a producer function, which takes in the value of the base model and returns an appropriate validator.

Examples

The documentation page for the .setValidator rule includes a full list of examples demonstrating the different overloads that are available.

These are all relevant to the .setAsyncValidator rule too, just replace Validator with AsyncValidator and .setValidator with .setAsyncValidator.

Nested validator does not depend on the base model

In this example the nested validator has no dependency on the base model, so we can simply define an instance of the nested validator ahead of time and return that from the validator producer function.

import { AsyncValidator } from 'fluentvalidation-ts';

type ContactDetails = {
  name: string;
  emailAddress: string;
};

class ContactDetailsValidator extends AsyncValidator<ContactDetails> {
  constructor() {
    super();

    this.ruleFor('name').notEmpty();

    this.ruleFor('emailAddress')
      .emailAddress()
      .mustAsync(
        async (emailAddress) => await api.emailAddressNotInUse(emailAddress)
      )
      .withMessage('This email address is already in use');
  }
}

const contactDetailsValidator = new ContactDetailsValidator();

type FormModel = {
  contactDetails: ContactDetails;
};

class FormValidator extends AsyncValidator<FormModel> {
  constructor() {
    super();

    this.ruleFor('contactDetails').setAsyncValidator(
      () => contactDetailsValidator
    );
  }
}

const formValidator = new FormValidator();

await formValidator.validateAsync({
  contactDetails: { name: 'Alex', emailAddress: 'alex123@example.com' },
});
// ✔ {}

await formValidator.validateAsync({
  contactDetails: { name: 'Alex', emailAddress: 'alex@example.com' },
});
// ❌ { contactDetails: { emailAddress: 'This email address is already in use' } }

Reference