How to validate a relation property in Laravel? - laravel

Question

What I have
I have a Room model with a has many relation to Reservation. Room has a property is_open indicating that the given room is available.
Goal
I would like to be able to validate in the rules function of a FormRequest that a room is available when I store a new reservation based on the is_open property.
What I tried
The validated data is in an array so the rule key needs to be this: data.room_id. I know that exists can validate something in the database but I don't know how its syntax works. Also how can I validate a property of a relation?
class ReservationStoreRequest extends FormRequest {
public function authorize() {
return true;
}
public function rules() {
return [
'data.room_id' => 'exists:' // what goes here?
];
}
}

Answer 1

tl;dr
public function rules() {
return [
'data.room_id' => [
Rule::exists('rooms', 'id')->where(function ($query) {
$query->where('is_open', 1);
})
]
];
}
Validating with exists
There is documentation on the exists rule but it is really concise. Lets see what the commands in the docs actually mean. The point of this rule is that it can validate the existence of a field in a table in your db given by some criteria. For example, when you save a reservation you can validate that the room you are reserving is exists in the database.
Basic usage
'size' => 'exists:rooms'
This will check the rooms table if there is an entry where the size column contains the value that is the value under validation (in this case the corresponding value of key size which is large). This results in the following SQL query:
select count(*) as aggregate from `rooms` where `size` = "large";
Specifying a custom column name
In the previous section the validated column's name comes from the key of the validated property ('size'). You might want to give a different column name because you are validating a column that is named differently from your data's key (e.g. 'size' is stored in the 'category' column) another case is that your rooms table's primary key is just id instead of room_id like in the validated data. In your case the validated data's key is data.room_id but you would like to check the id column of rooms. You can specify the column's name separated by a comma:
'data.room_id' => 'exists:rooms,id'
This will check the rooms table if there is an entry where the id column contains the value under validation resulting in the following SQL query:
select count(*) as aggregate from `rooms` where `id` = 4;
Specify a custom column name with extra clauses
If you need to further filter the results you can use the Illuminate\Validation\Rule class. You pass the table and column name (the second being optional just like in the basic usage section) and in an anonymous function add the extra clauses to the query. You can use every input data in the request, just retrieve it with $this->input('propertyName') or $this->all() then processing it by hand:
'data.room_id' => [
Rule::exists('rooms', 'id')->where(function ($query) {
$query
->where('is_open', 1);
->where('size', $this->input('data.size'));
})
]
The resulting SQL query is this:
select count(*) as aggregate from `rooms` where `id` = 4 and (`is_open` = 1 and `size` = large);
The available clauses in the $query variable are where, whereNot, whereNull, whereNotNull, whereIn and whereNotIn. Check out the Illuminate/Validation/Rules/Exists class docs.