# How do I add custom data to a transformer?

You can add a custom field using the `add()` method and returning an array:

```php
\Aero\Admin\Transformers\ProductTransformer::add(function ($data) {
   /* @var \Aero\Catalog\Models\Product */
   $product = $data['product'];

   return [
       'foo' => 'bar',
   ];
});
```

You can add a cast using the `addCast()` method:

```php
\Aero\Admin\Transformers\ProductTransformer::addCast('acme', 'integer');
```