Dependent fields are created by invoking the dependsOn method when defining a field. The dependsOn method accepts an array of dependent field attributes and a closure that modifies the configuration of the current field instance. Dependent fields allow advanced customization, such as toggling read-only mode, validation rules, and more based on the state of another field: 
use Laravel\Nova\Fields\FormData;
use Laravel\Nova\Fields\Select;
use Laravel\Nova\Fields\Text;
use Laravel\Nova\Http\Requests\NovaRequest;

// ...

return [
    Select::make('Purchase Type', 'type')
        ->options([
            'personal' => 'Personal',
            'gift' => 'Gift',
        ]),

    // Recipient field configuration is customized based on purchase type...
    Text::make('Recipient')
        ->readonly()
        ->dependsOn(
            ['type'],
            function (Text $field, NovaRequest $request, FormData $formData) {
                if ($formData->type === 'gift') {
                    $field->readonly(false)->rules(['required', 'email']);
                }
            }
        ),
];
To define dependent fields separately for creating and updating resources, you may use the dependsOnCreating and dependsOnUpdating methods.

​
Supported Dependent Fields

The following field types may depend on other fields:
  • Audio
  • BelongsTo
  • Boolean
  • BooleanGroup
  • Color
  • Code
  • Country
  • Currency
  • Date
  • DateTime
  • File
  • Heading
  • Hidden
  • Image
  • KeyValue
  • Markdown
  • MorphTo
  • Number
  • Password
  • PasswordConfirmation
  • Select
  • Status
  • Textarea
  • Text
  • Timezone
  • Trix
  • URL
  • VaporAudio
  • VaporFile
  • VaporImage
The following field types may not be depended upon by other fields since they do not live-report their changes to Nova:
  • Audio
  • Code
  • File
  • Image
  • KeyValue
  • Status
  • Tag
  • Trix
  • VaporAudio
  • VaporFile
  • VaporImage

​
Toggling Field Visibility Using dependsOn

One common use-case for dependent fields is toggling field visibility based on the value of another field. You can accomplish this using the hide and show methods: 
use Laravel\Nova\Fields\Boolean;
use Laravel\Nova\Fields\BelongsTo;
use Laravel\Nova\Fields\FormData;
use Laravel\Nova\Http\Requests\NovaRequest;

// ...

Boolean::make('Anonymous Comment', 'anonymous')
    ->onlyOnForms()
    ->fillUsing(fn () => null)
    ->default(true),

BelongsTo::make('User')
    ->hide()
    ->rules('sometimes')
    ->dependsOn('anonymous', function (BelongsTo $field, NovaRequest $request, FormData $formData) {
        if ($formData->boolean('anonymous') === false) {
            $field->show()->rules('required');
        }
    }),

​
Setting a Field’s Value Using dependsOn

Another common use-case for dependent fields is to set the value of a field based on the value of another field. You can accomplish this using the setValue method: 
use Laravel\Nova\Fields\DateTime;
use Laravel\Nova\Fields\FormData;
use Laravel\Nova\Http\Requests\NovaRequest;

// ...

DateTime::make('Created At'),

DateTime::make('Updated At')
    ->dependsOn(['created_at'], function (DateTime $field, NovaRequest $request, FormData $form) {
        $field->setValue(Carbon::parse($form->created_at)->addDays(7));
    }),

​
Accessing Request Resource IDs

When interacting with dependent fields, you may retrieve the current resource and related resource IDs via the resource method: 
BelongsTo::make(__('Books'), 'books', Book::class),

Currency::make('Price')
    ->dependsOn('books', function (Currency $field, NovaRequest $request, FormData $formData) {
        $bookId = (int) $formData->resource(Book::uriKey(), $formData->books);

        if ($bookId == 1) {
            $field->rules([
                'required', 'numeric', 'min:10', 'max:199'
            ])->help('Price starts from $10-$199');

            return;
        }

        $field->rules([
            'required', 'numeric', 'min:0', 'max:99'
        ])->help('Price starts from $0-$99');
    }),