How to use proxy with input field?

[zaibon]

Hi,

I would like to create an input text field that is meant to contains a coma separate string of items.
The underlying schema expect a list of string, one for each item. My guess is I need to use a superform proxy for it.
How can I pass the proxy to the Input component?

Example of what I'm tring to achieve:

export const schema = z.object({
    id: z.number().optional(),
    categories: z.array(z.string()),
});

...
<Form.Field {config} name="categories">
	<Form.Item>
		<Form.Label>Categories</Form.Label>
		<Form.Input />
		<Form.Validation />
	</Form.Item>
</Form.Field>
...

The problem here is that, as expected, the categories field receive a string when submitting the field.
I'm trying to use something like

<Form.Input 
on:input={(e) => {
	$form.categories = e.target.value.split(',');
}}
/>

But it does not seem to work.

Any recommendation on how to achieve this?