Symfony 6.2表单渲染失败：FormView无法转换为字符串

报错信息：

Object of class Symfony\Component\Form\FormView could not be converted to string

用户已尝试Symfony 6.2文档中的新方法（直接传入FormInterface）和旧的createView()方法，均触发相同报错，以下是相关代码：

控制器代码 #

#[Route(path: '/register', name: 'security-register')]
public function register(Request $request, MailUtil $util): Response
{
    $form = $this->createForm(RegistrationForm::class);
    $form->handleRequest($request);
    if($form->isSubmitted() && $form->isValid()){
        $mail = new Mail();
        $mail->setRecpient($form->get('email')->getData());
        $mail->setTemplate("TestMail");
        $util->sendMail($mail);
    }

    return $this->render("security/register.html.twig", ['form' => $form->createView()]);
}

表单类代码 #

class RegistrationForm extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options): void
    {
        $builder->add('email', EmailType::class, [
            'required' => true
            ])
            ->add('password', RepeatedType::class, [
                'type' => PasswordType::class,
                'invalid_message' => 'register.error.password',
                'required' => true,
                'first_options' => ['label' => 'Password'],
                'second_options' => ['label' => 'Repeat password']
            ])
            ->add('submit', SubmitType::class);
    }

    public function configureOptions(OptionsResolver $resolver)
    {
        $resolver->setDefaults([
            'csrf_protection' => true,
            'csrf_field_name' => '_csrf',
            'csrf_token_id' => 'user_register'
        ]);
    }
}

Twig模板代码 #

{% block container %}
    <div class="row">
        <div class="col s6 offset-s3">
            <div class="card-panel blue-grey darken-1" data-darkmode="card-panel blue-grey darken-3">
                {% if not app.user %}
                    <h4 class="white-text center-align ">
                        Register
                    </h4>
                    {{ form_start(form) }}
                    {{ form.email }}
                    {{ form_end(form) }}
                    <div class="white-text center-align">
                        You are logged in as {{ app.user.userIdentifier }}<br><br><a class="waves-effect waves-light btn" href="{{ path('app_logout') }}">Logout</a>
                    </div>
                {% endif %}
            </div>
        </div>
    </div>
{% endblock %}

问题原因与解决方法 #

问题出在Twig模板的{{ form.email }}这一行：直接访问form.email得到的是FormView对象，Twig会尝试将其转换为字符串输出，从而触发报错。

Symfony表单在Twig中必须使用专门的表单函数渲染字段：

• 渲染完整字段（含标签、输入框、错误提示）：{{ form_row(form.email) }}
• 仅渲染输入框部分：{{ form_widget(form.email) }}

修改后的模板核心代码示例：

{{ form_start(form) }}
{{ form_row(form.email) }}
{{ form_row(form.password) }}
{{ form_row(form.submit) }}
{{ form_end(form) }}

另外，模板中存在逻辑矛盾：{% if not app.user %}块内同时显示注册表单和登录后的注销信息，建议调整该部分逻辑避免混淆。

内容的提问来源于stack exchange，提问作者inao