Filament: Show/Hide Field Based on Select Value with Relationship Column

Imagine you have a Filament form with Select and Input fields, where that second Input should be visible only if a particular Select item is chosen. In addition, the condition is defined in a DB column from that Select relationship table. How to do it?

Imagine a form for a Company where you need to fill in the name, the country and enter a VAT number only for the countries that require it.

Imagine this DB structure:

countries

• name
• needs_vat (boolean, default false)

companies

• name
• country_id (foreign key)
• vat_number (string, optional)

Filament form code where that VAT Number field is always visible:

app/Filament/Resources/CompanyResource.php:

public static function form(Form $form): Form
{
    return $form
        ->schema([
            Forms\Components\TextInput::make('name')
                ->columnSpanFull(),
            Forms\Components\Select::make('country_id')
                ->relationship('country', 'name'),
            Forms\Components\TextInput::make('vat_number'),
        ]);
}

According to the official Filament documentation, to show/hide a field, we need to use the ->live() method on the first field and can use the ->visible() method on the second field, with a callback function condition and $get() value.

Checkbox::make('is_company')
    ->live()
 
TextInput::make('company_name')
    ->hidden(fn (Get $get): bool => ! $get('is_company'))

But our case is more complicated: how do we do that with a relationship column from the Select?

Our $get('country_id') would not return the needs_vat value.

One of the options is to query it from the database ourselves. Here's the updated working code:

app/Filament/Resources/CompanyResource.php:

public static function form(Form $form): Form
{
    return $form
        ->schema([
            Forms\Components\TextInput::make('name')
                ->columnSpanFull(),
            Forms\Components\Select::make('country_id')
                ->relationship('country', 'name')
                ->live(), 
            Forms\Components\TextInput::make('vat_number')
                ->visible( 
                    fn($record, $get) => Country::query() 
                        ->where([ 
                            'id' => $get('country_id'), 
                            'needs_vat' => 1 
                        ])->exists() 
                ), 
 
        ]);
}

If you want more Filament examples, you can find more real-life projects on our FilamentExamples.com.