public function rules()
    {
        $name = request('name');
        $city_id = request('city_id');
        return [
            'city_id' => 'required|integer|exists:cities,id',
            'name' => ['required','string', Rule::unique('companies')->where(function ($query) use ($name,$city_id) {
                return $query -> where('name',$name) -> where('city_id',$city_id);
            })]
        ];
    }