Symfony CollectionType中如何用数据对象属性作为字段标签？

问题场景 #

在Symfony框架中，使用CollectionType嵌套ShapeFractionType构建表单时，尝试通过options['data']获取ShapeFraction对象的name属性作为value字段的标签，出现'data'索引不存在的错误。直接使用ShapeFractionType时该逻辑正常，需实现每个输入框以对应ShapeFraction的name作为标签的效果，例如“A: <输入框>、B: <输入框>”。

相关代码 #

主表单类ShapeType #

class ShapeType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {        
        $builder->add('shape_fractions', CollectionType::class, [
            'entry_type' => ShapeFractionType::class,
            'entry_options' => ['label' => false],
        ]);
    }

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

Shape数据类 #

class Shape
{
    public array $shape_fractions;
       
    // ... 其他代码
}

ShapeFractionType类 #

class ShapeFractionType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        // 集合模式下'data'索引不可用，此处报错
        $shapeFraction = $options['data'];

        $builder
            ->add('value', NumberType::class, [
                'label' => $shapeFraction->name // 错误发生位置
            ]);
    }

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

ShapeFraction数据类 #

class ShapeFraction
{
    public string $name;
    public string $type;
    public float $value;

    // ... 其他代码
}

表单渲染代码 #

$shapeFractions = [
    new ShapeFraction('A', 'length', 10),
    new ShapeFraction('B', 'length', 20),
];
$shape = new Shape($shapeFractions);
$form = $formFactory->create(ShapeType::class, $shape);

// 使用Twig渲染表单...

解决方案 #

方法一：通过entry_options回调动态传递标签 #

在ShapeType中配置CollectionType时，利用回调函数将每个子项的name传递给ShapeFractionType：

class ShapeType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {        
        $builder->add('shape_fractions', CollectionType::class, [
            'entry_type' => ShapeFractionType::class,
            'entry_options' => function (FormInterface $child, $index) {
                /** @var ShapeFraction $shapeFraction */
                $shapeFraction = $child->getData();
                return [
                    'label' => $shapeFraction->name,
                ];
            },
        ]);
    }

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

修改ShapeFractionType直接使用传入的标签：

class ShapeFractionType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            ->add('value', NumberType::class, [
                'label' => $options['label'],
            ]);
    }

    public function configureOptions(OptionsResolver $resolver): void
    {
        $resolver->setDefaults([
            'data_class' => ShapeFraction::class,
            'label' => '', // 设置默认标签避免报错
        ]);
    }
}

方法二：利用FormEvents动态设置标签 #

在ShapeFractionType中监听PRE_SET_DATA事件，待数据绑定后设置标签：

use Symfony\Component\Form\FormEvent;
use Symfony\Component\Form\FormEvents;

class ShapeFractionType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder->add('value', NumberType::class);

        // 数据加载完成后设置标签
        $builder->addEventListener(FormEvents::PRE_SET_DATA, function (FormEvent $event) {
            /** @var ShapeFraction $shapeFraction */
            $shapeFraction = $event->getData();
            $form = $event->getForm();
            
            $form->add('value', NumberType::class, [
                'label' => $shapeFraction->name,
            ]);
        });
    }

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

方法三：Twig模板手动渲染标签 #

无需修改表单类，直接在视图层控制显示：

{% for fraction in form.shape_fractions %}
    <label>{{ fraction.vars.data.name }}:</label>
    {{ form_widget(fraction.value) }}
{% endfor %}

问题原因 #

使用CollectionType时，Symfony初始化子表单阶段尚未完成数据绑定，此时options['data']不存在；而单独使用ShapeFractionType时，表单初始化已绑定数据，因此可正常获取。

内容的提问来源于stack exchange，提问作者sanderbee