Symfony UX Live Components: "Expected string, null given"

Question

I'm using Symfony UX Live Components to edit an NtExam. I get this error when editing the form:

Expected argument of type "string", "null" given at property path "exam_title"

. Code Component:

#[AsLiveComponent]
class ExamEditComponent
{
    #[LiveProp(writable: true)]
    public ?NtExam $ntExam = null;

    public bool $showForm = false;

    public function __construct(private NtExamRepository $ntExamRepository) {}

    public function instantiateForm(): FormInterface
    {
        $exam = $this->ntExam ?? new NtExam();
        return $this->createForm(NtExamType::class, $exam);
    }

    #[LiveAction]
    public function editExam(#[LiveArg] int $id)
    {
        $this->ntExam = $this->ntExamRepository->find($id);
        $this->showForm = true;
    }
}

Edit Button

                <button class="nt-btn-grey" data-action="live#action" data-live-action-param="editExam"
                    data-live-id-param="{{ nt_exam.id }}">{{ ux_icon('lucide:file-pen-line',{height :
                    '16px'}) }}
                    <span>Edit</span></button>

Form Type (NtExamType):

class NtExamType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options): void
    {
        $builder->add('exam_title', TextType::class);
    }

    public function configureOptions(OptionsResolver $resolver): void
    {
        $resolver->setDefaults(['data_class' => NtExam::class]);
    }
}

Template: twig

<div>
    {% if component.showForm %}
        {{ form_start(form) }}
        {{ form_row(form.exam_title) }}
        {{ form_end(form) }}
    {% endif %}
</div>

Issue The ntExam object has a valid exam_title (confirmed via dd), but form update send null, causing the error.

Julian Koster · Accepted Answer · 2025-09-12 16:29:37Z

0

Set the button type to "button", otherwise the UX Live Component will interpret tue button type as a submit, trying to submit the form, so it becomes:

                <button type="button" class="nt-btn-grey" data-action="live#action" data-live-action-param="editExam"
                    data-live-id-param="{{ nt_exam.id }}">{{ ux_icon('lucide:file-pen-line',{height :
                    '16px'}) }}
                    <span>Edit</span></button>

answered Sep 12 at 16:29

Julian Koster

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