Laravel validation: rules in required_if - php

Question

I have a select list, where the first option is disabled, that's way when the user does not choose an valid option, the result of the select list will not be in the request.
In the validation, the field required, if the value of an other field is for example : 1, in case not 1, the field is not required.
The code:
'city_id' => [
'required',
'integer',
Rule::in(City::availableCities()),
],
'district_id' => new DistrictValidation(request('city_id')),
How I can do that, the district_id throw the validation every time, regardless of, it is in the request, or not.
Thanks for answers,
Update:
Maybe you see clearly, if the DistrictValidation rule is here:
class DistrictValidation implements Rule
{
protected $city;
private $messages;
/**
* Create a new rule instance.
*
* #param $cityId
*/
public function __construct($cityId)
{
$this->city = City::find($cityId);
}
/**
* Determine if the validation rule passes.
*
* #param string $attribute
* #param mixed $value
* #return bool
*/
public function passes($attribute, $value)
{
dd('here');
if (!$this->city) {
return false;
}
if (!$this->city->hasDistrict) {
return true;
}
$validator = Validator::make([$attribute => $value], [
$attribute => [
'required',
'integer',
Rule::in(District::availableDistricts()),
]
]);
$this->messages = $validator->messages();
return $validator->passes();
}
/**
* Get the validation error message.
*
* #return string
*/
public function message()
{
return optional($this->messages)->first('district_id');
}
}

Answer 1

You can use required_if condition defined in laravel validation
Here is the link to the proper documentaion Laravel Validation
Validator::make($data, [
'city_id' => [
'required',
'integer',
Rule::in(City::availableCities()),
],
'district_id'=>[
'required_with:city_id,',
]
]);

Answer 2

Try this:
'city_id' => [
'nullable',
'numeric',
Rule::in(City::availableCities())
],
'district_id' => new DistrictValidation(request('city_id')),

Answer 3

try this :
$myValidations = [
"city_id" => [
"required",
"integer"
]
]
// if city_id exists in availableCities so add some rules
if(collect(city::availableCities)->contains(request("city_id"))){
$myValidations["district_id"] = new DistrictValidation(request('city_id'))
}
// validate request fields with $myValidations variable

Answer 4

try using the required_if validation where the field under validation must be present and not empty if the anotherfield field is equal to any value.
required_if:field,value,...
use it like:
$request->validate([
'city_id' => 'required|integer|Rule::in(City::availableCities())',
'district_id' => 'required_if:city_id,1',
]);
try to read more laravel validation here