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Transformer Usage ​

Transform a result list ​

The common flow is to fetch records in a service and map them through a transformer.

php
use Quantum\Transformer\Contracts\TransformerInterface;

class PostTransformer implements TransformerInterface
{
    public function transform($item): array
    {
        return [
            'uuid' => $item->uuid,
            'title' => $item->title,
            'updated_at' => $item->updated_at,
        ];
    }
}

$payload = transform($posts, new PostTransformer());

This keeps response shaping separate from query or domain logic.

Reuse one transformer instance across a collection ​

php
$transformer = new PostTransformer();

$list = transform($posts, $transformer);
$featured = transform($featuredPosts, $transformer);

The package passes the same transformer object through the full collection mapping. That fits stateless transformers well and also works for transformers that carry shared formatting context.

Choose the right path for one record ​

The package focuses on collection mapping. For one record, call the transformer directly when that reads better in your code.

php
$item = $posts[0];
$payload = (new PostTransformer())->transform($item);

If you want to keep the same collection-shaped flow, wrap the item and read the first transformed value.

php
$payload = transform([$item], new PostTransformer())[0];

Preserve or reindex keys intentionally ​

transform() uses PHP array mapping semantics, so associative keys stay attached to their transformed values.

php
$byUuid = [
    'a1' => $postA,
    'b2' => $postB,
];

$transformed = transform($byUuid, new PostTransformer());
// keys remain: a1, b2

If you want sequential numeric keys, normalize the input first.

php
$transformed = transform(array_values($byUuid), new PostTransformer());

Convert iterables before mapping ​

The package works with arrays. When your data source returns another iterable type, convert it before calling the helper.

php
$payload = transform(iterator_to_array($items), new PostTransformer());

Keep output shape predictable ​

The interface accepts any return value, so the clearest application code comes from returning one consistent structure for each item in the same collection.

Empty collections flow through cleanly ​

An empty input array returns an empty array, which makes the helper a good fit for response pipelines that already expect a collection result.