select the old value with select input in laravel 8 blade - laravel

Question

how to make the old value selected in Laravel 8 blade with select input in edit form.... i tried this way but didn't work:
<select name="category" id="category" class=" #error('category') border-red-500 #enderror rounded-md shadow-sm mt-1 block w-full">
#foreach($categories as $category)
<option value="{{$category->id}}" {{ old('category', $category->id) ? 'selected' : '' }}>{{ $category->name }}</option>
#endforeach
</select>
and this is what inside controller:
public function edit(Product $product)
{
$categories = Category::all();
return view('dashboard.products.edit', compact('categories', 'product'));
}

Answer 1

I think your product should have a category_id so in the loop you need to check it also $product->category_id === $category->id.
#foreach($categories as $category)
<option value="{{$category->id}}" {{ old('category', $category->id) || $product->category_id === $category->id ? 'selected' : '' }}>{{ $category->name }}</option>
#endforeach
Based on the code in edit() method old() wont work. Because there is no old values since your code just return a view.If you need to use that function then you need to redirect with inputs like
return redirect()->back()->withInput();