如何使用 ZF3 设置延迟加载（任何地方都没有 ServiceLocator 模式）

我正在编写一个新的 ZF2 应用程序。我注意到“从任何地方”调用服务的 ServiceLocator 使用模式已从 ZF3 中弃用。我想为ZF3编写代码。

我能够设置我的控制器在构造函数时调用所有依赖项。但这意味着加载，即Doctrine在我需要它之前预先对象。

Question

如何设置它以便仅在我立即需要时才加载？ （延迟加载）。据我了解，ZF3 将加载移至控制器构造，这使得如何即时加载某些内容并不明显。

Old Code

class CommissionRepository
{

    protected $em;

    function getRepository()
    {
        //Initialize Doctrine ONLY when getRepository is called
        //it is not always called, and Doctrine is not always set up
        if (! $this->em)
            $this->em = $this->serviceLocator->get('doctrine');
        return $this->em;
    }
}

ServiceLocator 模式重构后的当前代码

class CommissionRepository
{

    protected $em;

    function getRepository()
    {
        return $this->em;
    }

    function setRepository($em)
    {
        $this->em = $em;
    }

    function useRepository($id)
    {
        return $this->em->find($id);
    }
}


class CommissionControllerFactory implements FactoryInterface
{

    public function createService(ServiceLocatorInterface $serviceLocator)
    {
        $parentLocator = $controllerManager->getServiceLocator();

        // set up repository
        $repository = new CommissionRepository();
        $repository->setRepository($parentLocator->get('doctrine'));

        // set up controller
        $controller = new CommissionController($repository);
        $controller->setRepository();

        return $controller;
    }
}

class CommissionController extends AbstractActionController
{

    protected $repository;

    public function setRepository(CommissionRepository $repository)
    {
        $this->repository = $repository;
    }

    public function indexAction()
    {
         //$this->repository already contains Doctrine but it should not
         //I want it to be initialized upon use.  How?
         //Recall that it has been set up during Repository construction time
         //and I cannot call it from "anywhere" any more in ZF3
         //is there a lazy loading solution to this?
         $this->repository->useRepository();
    }

如果您没有任何有效/强有力的理由来实例化自定义实体存储库，您应该更喜欢扩展Doctrine\ORM\EntityRepository在你的存储库中，例如CommissionRepository。例如;

use Doctrine\ORM\EntityRepository;

class CommissionRepository extends EntityRepository
{
    // No need to think about $em here. It will be automatically
    // injected by doctrine when you call getRepository().
    // 
    function fetchCommissionById($id)
    {
        // You can easily get the object manager directly (_em) or
        // using getEntityManager() accessor method in a repository
        return $this->_em->find($id);
    }
}

通过这种方式，当您调用时，实体管理器将在构建时自动注入到存储库中$em->getRepository('App\Entity\Commission') method.

我假设你已经有一个Commission您的应用程序中的实体Entity命名空间：

<?php
namespace App\Entity;

use Doctrine\ORM\Mapping as ORM;

/**
 * @ORM\Entity(repositoryClass="App\Repo\CommissionRepository")
 * @ORM\Table
 */
class Commission
{
}

然后您可以简化工厂中存储库的注入过程，例如：

// ZF2 Way
class CommissionControllerFactory implements FactoryInterface
{

    public function createService(ServiceLocatorInterface $services)
    {
        $em = $services->getServiceLocator()->get('doctrine');
        $repository = $em->getRepository('App\Entity\Commission');

        return new CommissionController($repository);
    }
}

UPDATE- 随着 Service Manager V3 的发布，FactoryInterface 已移至Zend\ServiceManager\Factory命名空间 (1)，工厂实际上是可调用的 (2)，并且可以与任何容器互操作 https://github.com/container-interop/container-interop兼容 DIC (3) 更新后的工厂如下所示：

// ZF3 Way
use Zend\ServiceManager\Factory\FactoryInterface;
use Interop\Container\ContainerInterface;
use Doctrine\ORM\EntityManager;

class CommissionControllerFactory implements FactoryInterface
{

    public function __invoke(ContainerInterface $dic, $name, array $options = null) {
        $em = $dic->get(EntityManager::class);
        $repository = $em->getRepository('App\Entity\Commission');

        return new CommissionController($repository);
    }
}

对于这个问题；正如马科什所说，懒惰服务 https://zendframework.github.io/zend-servicemanager/lazy-services/是在需要时立即创建服务的方法。 ZF3 发布后将使用 zend-servicemanager 3.0 组件。 （目前 zend-expressive 使用它）截至服务管理器 v3 https://github.com/zendframework/zend-servicemanager/releases?after=release-2.7.2您可以通过定义创建一些代理服务惰性服务 https://github.com/zendframework/zend-servicemanager/blob/f39c95385712ea5acb264aa3299c306423d768ed/src/ConfigInterface.php#L32-L40 and 代表者 https://zendframework.github.io/zend-servicemanager/delegators/在您的服务配置中：

'factories' => [],
'invokables' => [],
'delegators' => [
    FooService::class => [
        FooServiceDelegatorFactory::class,
    ], 
],
'lazy_services' => [
    // map of service names and their relative class names - this
    // is required since the service manager cannot know the
    // class name of defined services up front
    'class_map' => [
        // 'foo' => 'MyApplication\Foo',
    ],

    // directory where proxy classes will be written - default to system_get_tmp_dir()
    'proxies_target_dir' => null,

    // namespace of the generated proxies, default to "ProxyManagerGeneratedProxy"
    'proxies_namespace' => null,

    // whether the generated proxy classes should be written to disk or generated on-the-fly
    'write_proxy_files' => false,
];

另外，从服务管理器 v3 开始工厂 https://github.com/zendframework/zend-servicemanager/blob/master/src/Factory/FactoryInterface.php#L39兼容容器接口 https://github.com/container-interop/container-interop/。为了向前兼容，您可能需要保留两者__invoke() and createService()工厂中的顺利迁移方法。

最后，你的ZF3兼容工厂可能看起来像：

class CommissionControllerFactory implements FactoryInterface
{
    public function __invoke(ContainerInterface $container, $name, array $options = null)
    {
        $em = $container->get('doctrine');
        $repository = $em->getRepository('App\Entity\Commission');

        return new CommissionController($repository);
    }

    public function createService(ServiceLocatorInterface $container, $name = null, $requestedName = null)
    {
        return $this($container, $requestedName, []);
    }
}

希望能帮助到你。