如何解决PHP对象间繁琐的数据映射问题，使用SymfonyCastsMicroMapper让数据转换清晰可控

<pre class="brush:php;toolbar:false;">$dragon = $dragonRepository->find(1);
$dragonDTO = new DragonDTO();
$dragonDTO->id = $dragon->getId();
$dragonDTO->name = $dragon->getName();
// ... 如果有几十个属性，或者有嵌套对象，这简直是噩梦！

<code class="bash">composer require symfonycasts/micro-mapper</code>

<pre class="brush:php;toolbar:false;">// App/Entity/Dragon.php (假设的实体类)
namespace App\Entity;
class Dragon {
    private int $id;
    private string $name;
    private int $firePower;
    // ... getters
}

// App/DTO/DragonDTO.php (假设的DTO类)
namespace App\DTO;
class DragonDTO {
    public int $id;
    public string $name;
    public int $firePower;
    public function __construct(int $id) { $this->id = $id; }
}

// App/Mapper/DragonEntityToDtoMapper.php
namespace App\Mapper;

use App\Entity\Dragon;
use App\DTO\DragonDTO;
use Symfonycasts\MicroMapper\AsMapper;
use Symfonycasts\MicroMapper\MapperInterface;

#[AsMapper(from: Dragon::class, to: DragonDTO::class)]
class DragonEntityToDtoMapper implements MapperInterface
{
    /**
     * load() 方法负责创建或加载目标对象。
     * 通常在这里只设置标识符，或从数据库加载现有对象。
     */
    public function load(object $from, string $toClass, array $context): object
    {
        // 确保 $from 是 Dragon 实例
        assert($from instanceof Dragon); 
        return new DragonDTO($from->getId());
    }

    /**
     * populate() 方法负责将源对象的数据填充到目标对象中。
     * 在这里进行实际的属性赋值。
     */
    public function populate(object $from, object $to, array $context): object
    {
        // 确保类型正确
        assert($from instanceof Dragon);
        assert($to instanceof DragonDTO);

        $to->name = $from->getName();
        $to->firePower = $from->getFirePower();
        // ... 其他属性

        return $to;
    }
}

<pre class="brush:php;toolbar:false;"><?php
// App/Controller/DragonController.php
namespace App\Controller;

use App\Entity\Dragon;
use App\DTO\DragonDTO;
use Symfonycasts\MicroMapper\MicroMapperInterface;
use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
use Symfony\Component\Routing\Annotation\Route;

class DragonController extends AbstractController
{
    #[Route('/dragons/{id}', name: 'api_dragon_get')]
    public function show(Dragon $dragon, MicroMapperInterface $microMapper)
    {
        // 轻松将 Dragon 实体映射到 DragonDTO
        $dragonDTO = $microMapper->map($dragon, DragonDTO::class);

        return $this->json($dragonDTO);
    }
}

<pre class="brush:php;toolbar:false;">// App/Mapper/DragonEntityToDtoMapper.php (修改后)
namespace App\Mapper;

// ... other uses
use App\ApiResource\TreasureApi; // 假设 TreasureApi 是 Treasure 的 DTO
use Symfonycasts\MicroMapper\MicroMapperInterface;

#[AsMapper(from: Dragon::class, to: DragonDTO::class)]
class DragonEntityToDtoMapper implements MapperInterface
{
    public function __construct(private MicroMapperInterface $microMapper)
    {
    }

    // load() 方法保持不变

    public function populate(object $from, object $to, array $context): object
    {
        assert($from instanceof Dragon);
        assert($to instanceof DragonDTO);

        $to->name = $from->getName();
        $to->firePower = $from->getFirePower();

        $treasuresDtos = [];
        foreach ($from->getTreasures() as $treasureEntity) {
            // 递归映射 Treasure 实体到 TreasureDTO
            $treasuresDtos[] = $this->microMapper->map($treasureEntity, TreasureDTO::class, [
                // 关键点：MAX_DEPTH 用于控制深度，防止循环引用
                MicroMapperInterface::MAX_DEPTH => 1, 
            ]);
        }
        $to->treasures = $treasuresDtos;

        return $to;
    }
}

<pre class="brush:php;toolbar:false;">// App/Mapper/DragonApiToEntityMapper.php
namespace App\Mapper;

use App\ApiResource\DragonApi;
use App\Entity\Dragon;
use App\Repository\DragonRepository;
use Symfonycasts\MicroMapper\AsMapper;
use Symfonycasts\MicroMapper\MapperInterface;
use Symfonycasts\MicroMapper\MicroMapperInterface;
use Symfony\Component\PropertyAccess\PropertyAccessorInterface;

#[AsMapper(from: DragonApi::class, to: Dragon::class)]
class DragonApiToEntityMapper implements MapperInterface
{
    public function __construct(
        private DragonRepository $dragonRepository,
        private MicroMapperInterface $microMapper,
        private PropertyAccessorInterface $propertyAccessor // 注入 PropertyAccessor
    ) {
    }

    public function load(object $from, string $toClass, array $context): object
    {
        assert($from instanceof DragonApi);
        return $from->id ? $this->dragonRepository->find($from->id) : new Dragon();
    }

    public function populate(object $from, object $to, array $context): object
    {
        assert($from instanceof DragonApi);
        assert($to instanceof Dragon);

        $to->setName($from->name);
        $to->setFirePower($from->firePower);

        $treasureEntities = [];
        foreach ($from->treasures as $treasureApi) {
            $treasureEntities[] = $this->microMapper->map($treasureApi, Treasure::class, [
                MicroMapperInterface::MAX_DEPTH => 0, // 仅加载实体，不填充嵌套
            ]);
        }

        // 使用 PropertyAccessor 智能更新集合
        $this->propertyAccessor->setValue($to, 'treasures', $treasureEntities);

        return $to;
    }
}