We can leverage a FormRequest without actually submitting a form in two ways:

• Using the after hook on Validator instance
• Merging some data manually in the request and then validating it

Let's take a look at these.

After hook on Validator instance

class DestroyPostRequest extends FormRequest
{

    public function rules(): array
    {
        return [];
    }

    public function withValidator(Validator $validator): void
    {
        $validator->after(function ($validator) {
            if ($this->somethingElseIsInvalid()) {
                $validator->errors()->add('field', 'Something is wrong with this field!');
            }
        });
    }
}

In this case, rules method return an empty array since we don't have any fields against which we can perform validations.

By using the withValidator method, we are able to perform additional logic and add errors to the validator.

Merge data manually in request and then validate it

class DestroyPostRequest extends FormRequest
{

    public function prepareForValidation(): void
    {
        $this->merge([
            'post_id' => $this->route('id') 
        ]);
    }

    public function rules(): array
    {
        return [
            'post_id' => ['required', 'between:1,50']
        ];
    }
}

prepareForValidation allows us to intialize or sanitize the request data before validation rules are applied. We can also add some new data to request inside this method.

In above example, post_id field is being added to the request and then afterwards being validated inside the rules.

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