# How do I add setting definitions to a model?

Setting definitions allow you to define settings via the admin UI.

To add a setting definition for a model, you must add the model type, you can do this using the model class or relation key.

For example:

```php
// By class
\Aero\Common\Models\SettingDefinition::addModelType(Acme::class, 'Acme');

// By relation key
\Aero\Common\Models\SettingDefinition::addModelType(Acme::RELATION_KEY, 'Acme');
```

<p class="callout info">The model you're adding must support model settings for setting definitions to work.</p>