Dynamic select options from external api

TextInput::make('postal_code')
  ->label('Postleitzahl')
  ->required()
  ->afterStateUpdated(function (Get $get, ?string $state, Set $set) use ($serviceInstance) {
    if (strlen($state) === 5 && $get('country') === 'DE') {
      self::$cities = $serviceInstance->loadCities($state);
      
      if (isset(self::$cities['message'])) {
        Notification::make()
          ->title(self::$cities['message'])
          ->danger()
          ->send();
      }
      
      if (count(self::$cities) === 1) {
        $set('city', self::$cities[0]);
      }
    }
    
    if ($state === null) {
      $set('city', '');
    }
  })
  ->live(),
Select::make('city')
  ->label('Stadt/Ort')
  ->options(self::$cities)
  ->live()
  ->searchable()
  ->required(),

TextInput::make('postal_code')
    ->label('Postleitzahl')
    ->required()
    ->afterStateUpdated(function (?string $state, Set $set) {
        if ($state === null) {
            $set('city', '');
        }
    })
    ->reactive()
    ->live(),
Select::make('city')
    ->label('Stadt/Ort')
    ->options(function (Get $get) {
        if ($get('postal_code') !== null && strlen($get('postal_code') === 5)) {
            return GeoLocationHelper::getInstance()->loadCities($get('postal_code'));
        }
        
        return [];
    })
    ->reactive()
    ->required(),