[Proposal] Decouple mutators / attribute casting from the Eloquent ORM

Wouldn't be great to encapsulate the attributes manipulation? That could be very useful eg. in the Request class. Regarding casting I thought of something as simple as:

CastableContract
CastableTrait

abstract class Model implements ArrayAccess, Arrayable, Castable, Jsonable, JsonSerializable, QueueableEntity, UrlRoutable
{
    use CastableTrait;
    …
}

class Request extends SymfonyRequest implements Arrayable, ArrayAccess, Castable
{
    use CastableTrait, Macroable;
    …
}

In combination with custom casting discussed in https://github.com/laravel/framework/pull/16305 and https://github.com/laravel/framework/pull/13706 it could be a very powerfull and yet a clean solution. Another approach could be a Processor/Transformer implementation (this is just a basic idea inspired by the need to encapsulate request data processing):

Processable contract

interface Processable
{
/**
 * Get the processed contents of the object.
 *
 * @return mixed
 */
public function processed();
}

an object/array could be also easily processed with a processor composite:

class ProcessableStack extends \SplObjectStorage implements Processable
{
/**
 * Calculates an unique identifier for the contained processor.
 *
 * @param Processor $object
 *
 * @return string
 */
public function getHash($object): string
{
    return get_class($object);
}

/**
 * {@inheritdoc}
 */
public function processed()
{
    if (!$input = func_get_arg(0)) {
        return;
    }

    foreach ($this as $hash => $processor) {
        $input = $processor->run($input);
    }

    return $input;
}
}

examples of use:

$request->processedWith(UserUpdateRequest::class);
// or
$request->setProcessor(new UserUpdateRequest)->processed();
// or
$request->processed();

or maybe better interally by all(), input(), except() etc.?

laravel / framework

[Proposal] Decouple mutators / attribute casting from the Eloquent ORM #16377