How can I implement async validation in Angular forms?

How can I implement async validation in Angular forms?

You can implement async validation in Angular forms by using the AsyncValidatorFn interface. This allows you to create custom validators that return an observable.

Can you give me an example of an async validator?

Sure! Here's a simple example: you can create a validator that checks if a username is already taken by making an HTTP request to your server.

How do I attach this async validator to a form control?

You can attach it by using the setAsyncValidators method on the form control. For example: this.formControl.setAsyncValidators(yourAsyncValidatorFunction);.

What if I want to show a loading indicator while validating?

You can manage a loading state in your component and update it when the async validation starts and ends. This way, you can show a spinner or loading message.