LegacyModelAwareTrait

If your app makes heavy use of loadModel() calls, it can be helpful to first leave them in place when upgrading and take care of further changes later, once the app is confirmed to run again.

For this you can use this trait on top of the core ModelAwareTrait:

use Cake\Datasource\ModelAwareTrait;
use Shim\Datasource\LegacyModelAwareTrait;

/**
 * @property \Data\Model\Table\CountriesTable $Countries
 */
#[\AllowDynamicProperties]
class SomeController extends AppController {

    use ModelAwareTrait;
    use LegacyModelAwareTrait;

    public function someAction() {
        $this->loadModel('Data.Countries');

        $countries = $this->Countries->find()->...;
    }

}

It will continue to set the dynamic class property $Countries.

Required attribute

As shown above, it is important to set #[\AllowDynamicProperties] to avoid it blowing up in PHP 8.2+.

The docblock annotation with the actual class is helpful to get full IDE support and auto-complete. This should already be the case for your existing code, provided via the IdeHelper plugin.

Setting a custom model class

When setting a custom model class on a controller, the traits cannot be added to that same controller due to an inheritance collision if you are using the $modelClass property. So it would have to be on a parent controller, usually the AppController itself.

use Cake\Controller\Controller;
use Cake\Datasource\ModelAwareTrait;
use Shim\Datasource\LegacyModelAwareTrait;

/**
 * @property \Data\Model\Table\CountriesTable $Countries
 */
#[\AllowDynamicProperties]
class AppController extends Controller {

    use ModelAwareTrait;
    use LegacyModelAwareTrait;

}

and:

use App\Controller\AppController;

/**
 * @property \Data\Model\Table\CountriesTable $Countries
 */
class SomeController extends AppController {

    /**
     * @var string|null
     */
    protected ?string $modelClass = 'Data.Countries';

    public function someAction() {
        $countries = $this->Countries->find()->...;
    }

}

In cases where you cannot use the parent class — for example directly in some command or custom class — you can use the $defaultModel property instead:

    /**
     * @var string|null
     */
    protected ?string $defaultModel = 'Packages';

It will override any other set property for $this->loadModel() calls.

Autoloading models as before

If you want to completely retain 4.x behavior of autoloading the models, you need to add this snippet to your (App)Controller initialize() method, where you added the traits:

    if ($this->modelClass) {
        $this->loadModel();
    }