Validate a field only if another one passes validation

I have a form request that needs to validate 2 fields. However, I need to validate one of the fields only if the other one passes validation. I came up with something like this:

public function rules()
{
    return [
        'token' => ['bail', 'required', 'uuid', new ValidExchange],
    ];
}

public function withValidator($validator)
{
    $validator->after(function ($validator) {
        // This forces the validator to evaluate the rules defined in the rules() method above.
        if ($validator->failed()) return;

        // We only want to validate this field if the `token` rules were successful.
        // The `ValidExchange` injects the `product_id` into the request object, making it
        // available here, while IT IS NOT in the rules() method.
        // The `product_id` is known to us only after the `ValidExchange` rule is evaluated!
        Validator::make($this->input(), [
            'product_id' => ['required', new NoUnusedCards(auth()->id())]
        ])->validate();
    });
}

As the comment in the code says, the ValidExchange rule performs an API call to some external service, which returns an id that can be used to find a row in the database locally, from which we can get the product_id and inject it into the request object as follows:

request()->merge(['product_id' => $card->product_id]);

, as it too needs to be validated.

This works but doesn't feel right. Is there a cleaner way to do this or another approach that I might be missing? Thank you :)

Snapey

6 years ago

Level 122

restrict validation to checking the inputs (form or api) and check the product_id in the controller or otherwise.?

uhajzeraj

6 years ago

Level 14

@snapey Validating the product_id in the controller does work, but I feel that it kind of defeats the purpose of having a form request class. I would like the entire validation process to be done in the form request, and only if it succeeds, continue in the controller.

fylzero

6 years ago

Level 67

@uhajzeraj I don't really care where this lives. You could argue that both ways as to whether this is truly validation or logic.

That said. What part of how you're doing this "doesn't feel right"?

The answer to ugliness is comments and refactoring. Rather than just say, this doesn't seem right... try to answer why it doesn't seem right. If you can do that it will help assist answering the real question.

I personally would just ship it as you have it and comment/document it.

willvincent

6 years ago

Level 54

Might be a good candidate for a sometimes rule.

uhajzeraj

6 years ago

Level 14

@fylzero It doesn't feel right as I am doubtful if this case should be handled like this. Not entirely understanding what's going on in the withValidator method kind of adds to that feeling.

uhajzeraj

6 years ago

Level 14

@willvincent it must always be present if the token validation rules pass. With sometimes it won't validate, as it is not in the request object yet.

fylzero

6 years ago

Best Answer

Level 67

@uhajzeraj withValidator is specifically designed to use the after hook. Basically to run validation after other validation. This is probably the exact correct pattern for what you are doing. This exists in the Laravel docs.

See: Adding After Hooks to Form Requests (Just below this section)

https://laravel.com/docs/6.x/validation#creating-form-requests

Top-Master

4 years ago

Level 1

Since Laravel 5,6 we can try:

use Illuminate\Support\Facades\Validator;

// ...

public function rules()
{
    $result = [
        // ...
        'warehouse_id' => 'required|unique:warehouse,id',
    ];

    if (Validator::make($this->input(), $result)->passes()) {
        $result['warehouse_qty'] = [
            function ($attribute, $value, $fail) {
                if (empty($value)) {
                    $fail('The '.$attribute.' is required.');
                }
            },
        ];
    }

    return $result;
}

Note that for above to work, the fields order is important, and the closure should be in array right after the fields it is checking.