如何使用两个值的总和重定向我的表单并将其显示在Laravel的只读输入字段中？

Question

I am making a simple form two sum two values. I want to display the calculated result in an readonly input after the request went through. If I dd() the sum of my two fields, the sum is correct. But I am unable to pass the sum back to the view.

I searched around the web and found nothing promising. Same with the Laravel documentation.

Form:

<p>
<input type="number" name="numberOne" value="{{ old('numberOne') }}">
</p>
<p>
<input type="number" name="numberTwo" value="{{ old('numberTwo')}}">
</p>
<p>
<input type="number" name="calculated" value="{{ isset($calculated) ? $calculated : '' }}" readonly>
</p>

Controller:

class CalculationsController extends Controller
{
    public function process(Request $request) {
        $numberOne = $request->input('numberOne');
        $numberTwo = $request->input('numberTwo');

        $calculated = $numberOne + $numberTwo;

        dd($calculated);

        return redirect('/')->withInput();
    }
}

Expected would be the sum of both inputs in the readonly. But after the submit, it's still empty. What am I doing wrong?

Answer 1

When you use the redirect() function the variable $calculated isn't passed to the view. I think the best solution is passing it by Session. Your redirect must be something like that:

return redirect('/')->withInput()->with('calculated', $calculated);

The with() function is used to pass data through the session. To retrieve it in your view, do:

<input type="number" name="calculated" value="{{ session()->has('calculated') ? session('calculated') : '' }}" readonly>

For documentation, check: https://laravel.com/docs/5.7/redirects#redirecting-with-flashed-session-data https://laravel.com/docs/5.7/session#retrieving-data