Symfony Live ComponentsとUX 3.0：JavaScriptなしでリアクティブアプリを構築する方法（2026年版）

# terminal
composer require symfony/ux-live-component

# With AssetMapper (recommended for Symfony 7.4+)
php bin/console importmap:require @symfony/ux-live-component

# Verify installation
php bin/console debug:twig --filter=component

<?php
// src/Twig/Components/ProductSearch.php

namespace App\Twig\Components;

use App\Repository\ProductRepository;
use Symfony\UX\LiveComponent\Attribute\AsLiveComponent;
use Symfony\UX\LiveComponent\Attribute\LiveProp;
use Symfony\UX\LiveComponent\DefaultActionTrait;

#[AsLiveComponent]
class ProductSearch
{
    use DefaultActionTrait;

    // writable: true allows the frontend to modify this property
    // url: true syncs the value with ?query= in the address bar
    #[LiveProp(writable: true, url: true)]
    public string $query = '';

    #[LiveProp(writable: true)]
    public string $category = 'all';

    public function __construct(
        private ProductRepository $productRepository,
    ) {
    }

    public function getProducts(): array
    {
        if (strlen($this->query) < 2) {
            return [];
        }

        return $this->productRepository->search(
            query: $this->query,
            category: $this->category === 'all' ? null : $this->category,
            limit: 20,
        );
    }
}

{# templates/components/ProductSearch.html.twig #}
<div {{ attributes }}>
    <input
        type="search"
        data-model="debounce(300)|query"
        placeholder="Search products..."
        class="form-input w-full"
    />

    <select data-model="category" class="form-select mt-2">
        <option value="all">All categories</option>
        <option value="electronics">Electronics</option>
        <option value="books">Books</option>
    </select>

    <div class="mt-4">
        {% for product in this.products %}
            <div key="{{ product.id }}" class="border-b py-2">
                <h3>{{ product.name }}</h3>
                <span>{{ product.price|format_currency('EUR') }}</span>
            </div>
        {% else %}
            {% if query|length >= 2 %}
                <p>No results for "{{ query }}".</p>
            {% endif %}
        {% endfor %}
    </div>
</div>

<?php
// src/Twig/Components/ShoppingCart.php

namespace App\Twig\Components;

use App\Entity\CartItem;
use App\Service\CartService;
use Symfony\UX\LiveComponent\Attribute\AsLiveComponent;
use Symfony\UX\LiveComponent\Attribute\LiveAction;
use Symfony\UX\LiveComponent\Attribute\LiveArg;
use Symfony\UX\LiveComponent\Attribute\LiveProp;
use Symfony\UX\LiveComponent\ComponentToolsTrait;
use Symfony\UX\LiveComponent\DefaultActionTrait;

#[AsLiveComponent]
class ShoppingCart
{
    use DefaultActionTrait;
    use ComponentToolsTrait;

    #[LiveProp]
    public array $items = [];

    public function __construct(
        private CartService $cartService,
    ) {
    }

    #[LiveAction]
    public function addItem(#[LiveArg] int $productId, #[LiveArg] int $quantity = 1): void
    {
        $this->cartService->add($productId, $quantity);
        $this->items = $this->cartService->getItems();

        // Notify other components on the page
        $this->emit('cart:updated', [
            'count' => count($this->items),
        ]);
    }

    #[LiveAction]
    public function removeItem(#[LiveArg] int $itemId): void
    {
        $this->cartService->remove($itemId);
        $this->items = $this->cartService->getItems();
        $this->emit('cart:updated', ['count' => count($this->items)]);
    }

    public function getTotal(): float
    {
        return array_sum(array_map(
            fn(CartItem $item) => $item->getPrice() * $item->getQuantity(),
            $this->items,
        ));
    }
}

{# templates/components/ShoppingCart.html.twig #}
<div {{ attributes }}>
    <h2>Cart ({{ items|length }})</h2>

    {% for item in items %}
        <div key="{{ item.id }}" class="flex justify-between py-2">
            <span>{{ item.name }} x{{ item.quantity }}</span>
            <span>{{ (item.price * item.quantity)|format_currency('EUR') }}</span>
            <button {{ live_action('removeItem', { itemId: item.id }) }}
                    class="text-red-600">
                Remove
            </button>
        </div>
    {% endfor %}

    <div class="border-t pt-2 font-bold">
        Total: {{ this.total|format_currency('EUR') }}
    </div>
</div>

<?php
// src/Twig/Components/RegistrationForm.php

namespace App\Twig\Components;

use App\Entity\User;
use App\Form\RegistrationType;
use Doctrine\ORM\EntityManagerInterface;
use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
use Symfony\Component\Form\FormInterface;
use Symfony\UX\LiveComponent\Attribute\AsLiveComponent;
use Symfony\UX\LiveComponent\Attribute\LiveAction;
use Symfony\UX\LiveComponent\Attribute\LiveProp;
use Symfony\UX\LiveComponent\ComponentWithFormTrait;
use Symfony\UX\LiveComponent\DefaultActionTrait;

#[AsLiveComponent]
class RegistrationForm extends AbstractController
{
    use DefaultActionTrait;
    use ComponentWithFormTrait;

    #[LiveProp]
    public ?User $initialFormData = null;

    protected function instantiateForm(): FormInterface
    {
        return $this->createForm(RegistrationType::class, $this->initialFormData ?? new User());
    }

    #[LiveAction]
    public function save(EntityManagerInterface $em): mixed
    {
        // Submits + validates — re-renders with errors if invalid
        $this->submitForm();
        $user = $this->getForm()->getData();

        $em->persist($user);
        $em->flush();

        $this->addFlash('success', 'Account created.');

        return $this->redirectToRoute('app_login');
    }
}

{# templates/components/RegistrationForm.html.twig #}
<div {{ attributes }}>
    {{ form_start(form, {
        attr: {
            'data-action': 'live#action:prevent',
            'data-live-action-param': 'save'
        }
    }) }}
        {{ form_row(form.email) }}
        {{ form_row(form.plainPassword, { label: 'Password' }) }}
        {{ form_row(form.fullName) }}

        <button type="submit"
                class="btn-primary w-full"
                data-loading="addAttribute(disabled) addClass(opacity-50)">
            <span data-loading="hide">Create Account</span>
            <span data-loading="show" class="animate-spin">Loading...</span>
        </button>
    {{ form_end(form) }}
</div>

<?php
// src/Twig/Components/AnalyticsDashboard.php

namespace App\Twig\Components;

use App\Service\AnalyticsService;
use Symfony\UX\LiveComponent\Attribute\AsLiveComponent;
use Symfony\UX\LiveComponent\Attribute\LiveProp;
use Symfony\UX\LiveComponent\DefaultActionTrait;

#[AsLiveComponent]
class AnalyticsDashboard
{
    use DefaultActionTrait;

    #[LiveProp]
    public string $period = '30d';

    public function __construct(
        private AnalyticsService $analytics,
    ) {
    }

    public function getMetrics(): array
    {
        // Expensive query — runs only after page load
        return $this->analytics->getMetrics($this->period);
    }
}

{# Parent page: load the dashboard after the page renders #}
<twig:AnalyticsDashboard loading="defer" period="30d" />

{# Or load when scrolled into view #}
<twig:AnalyticsDashboard loading="lazy" period="30d" />

{# templates/components/AnalyticsDashboard.html.twig #}
<div {{ attributes }}>
    <h2>Analytics — {{ period }}</h2>
    {% for metric in this.metrics %}
        <div class="stat-card">
            <span class="stat-label">{{ metric.label }}</span>
            <span class="stat-value">{{ metric.value|number_format }}</span>
        </div>
    {% endfor %}
</div>

{% macro placeholder(props) %}
    <div class="animate-pulse space-y-4">
        <div class="h-6 bg-gray-200 rounded w-1/3"></div>
        <div class="h-20 bg-gray-200 rounded"></div>
        <div class="h-20 bg-gray-200 rounded"></div>
    </div>
{% endmacro %}

<?php
// src/Twig/Components/CartBadge.php

namespace App\Twig\Components;

use App\Service\CartService;
use Symfony\UX\LiveComponent\Attribute\AsLiveComponent;
use Symfony\UX\LiveComponent\Attribute\LiveListener;
use Symfony\UX\LiveComponent\Attribute\LiveProp;
use Symfony\UX\LiveComponent\DefaultActionTrait;

#[AsLiveComponent]
class CartBadge
{
    use DefaultActionTrait;

    #[LiveProp]
    public int $count = 0;

    public function __construct(CartService $cartService)
    {
        $this->count = $cartService->getItemCount();
    }

    // Automatically re-renders when ShoppingCart emits 'cart:updated'
    #[LiveListener('cart:updated')]
    public function onCartUpdated(#[LiveArg] int $count): void
    {
        $this->count = $count;
    }
}