laravel how to add validation rule based on custom database query - laravel

Question

I want the user to input postal code then in register controller I want to validate that postal code against postal code database I have so if the user provided postal code is in my database it will success despite of the formatting he/she used and what I mean by that is I want the validation to success whether he/she use spaces or no spaces at all.
the query I would like to use:
$postalcode=$data['postal_code'];
zipcodes::whereRaw('replace(POSTAL_CODE,\' \',\'\')=? ',[str_replace(' ','',$postal_code)
I tried to use the following in my validation:
Rule::exists('zipcodes','POSTAL_CODE')->where(function ($query) use($postalcode) {
// die($postalcode);
$query->whereRaw('replace(POSTAL_CODE,\' \',\'\')=? ',[str_replace(' ','',$postalcode)]);
})
but it does not do what I want and it seems to already try to find if postal code exist in zipcodes table before performing mysql replace or php str_replace.
so please any suggestions?

Answer 1

The easiest way to do this is use Laravel's validate() method.
https://laravel.com/docs/5.7/validation
You can use the Exists validation rule. It will check the database you tell it to and if the record exists, if it does then it will show as valid.
If you need to trim the spaces before validation, first just do $request->postal_code = str_replace(' ', '', $request->postal_code); before you call the validate method.
Here is a complete example:
$request->postal_code = str_replace(' ', '', $request->postal_code);
$request->validate([
'postal_code' => 'required|exists:zipcodes',
]);