6.2 加载实体
加载实体
查询对象的 execute() 方法只是返回实体 ID 数组。要使用这些实体我们必须加载这些实体对象。Drupal 7 使用 entity_load() 函数返回一个实体对象数组（基于传递给它的 ID 数组）。Drupal 8 里这个函数变为只返回一个实体对象（当然参数也不再是 ID 数组，而只是一个 ID），而额外又提供了一个加载多个实体的方法： entity_load_multiple() 。
有三种方法加载实体：
类方法（推荐）
依赖注入将在之后章节讨论。代码中的重要部分是 example() 方法，它使用 entityManager 对象构建了一个节点存储对象。之后我们使用这个存储对象获得一个节点对象或者节点对象列表。
protected $entityManager;
/**
* {@inheritdoc}
*/
public function __construct(EntityManagerInterface $entityManager) {
$this->entityManager = $entityManager;
}
/**
* {@inheritdoc}
*/
public static function create(ContainerInterface $container) {
return new static(
$container->get('entity.manager')
);
}
/**
* Return a list of nodes that are published.
*/
protected function example() {
// We get the node storage object.
$node_storage = $this->entityManager->getStorage('node');
// We use the load function to load a single node object.
$nid = 1;
$node = $node_storage->load($nid);
// We load a revision
$revision_id = 1;
$node = $node_storage->loadRevision($revision_id);
// We use the loadMultiple function to load an array of node objects keyed
// by node ID.
$nids = [1,2,3,4];
$nodes = $node_storage->loadMultiple($nids);
// We will discuss this in future lessons, but you can get the value of
// simple fields using ->get('field_name')->value.
return [
'#markup' => $node->get('title')->value,
];
}
静态方法（不推荐）
当容器无效时，你也可以使用静态方法。
// Get a node storage object.
$node_storage = \Drupal::entityManager()->getStorage('node');
// Load a single node.
$node_storage->load($nid);
// Load multiple nodes.
$node_storage->loadMultiple($nids);
全局方法（不推荐）
全局方法类似 Drupal 7。
// Load a single entity.
$node = entity_load('node', $nid);
// Load multiple entities.
$nodes = entity_load_multiple('node', $nids);
创建控制器
我们把这些碎片汇总下。使用例子模块，在 QueryExampleController.php 的方法内追加查询对象获得节点 ID。
<?php
/**
* @file
* Contains \Drupal\query_example\Controller\QueryExampleController.
*/
namespace Drupal\query_example\Controller;
use Drupal\Core\Entity\Query\QueryFactory;
use Symfony\Component\DependencyInjection\ContainerInterface;
use Drupal\Core\Controller\ControllerBase;
/**
* Controller routines for page example routes.
*/
class QueryExampleController extends ControllerBase {
protected $entity_query;
public function __construct(QueryFactory $entity_query) {
$this->entity_query = $entity_query;
}
public static function create(ContainerInterface $container) {
return new static(
$container->get('entity.query')
);
}
protected function simpleQuery() {
$query = $this->entity_query->get('node')
->condition('status', 1);
$nids = $query->execute();
return array_values($nids);
}
public function basicQuery() {
return [
'#title' => 'Published Nodes',
'content' => [
'#theme' => 'item_list',
'#items' => $this->simpleQuery()
]
];
}
protected function intermediateQuery() {
$query = $this->entity_query->get('node')
->condition('status', 1)
->condition('changed', REQUEST_TIME, '<')
->condition('title', 'ipsum lorem', 'CONTAINS')
->condition('field_tags.entity.name', 'test');
$nids = $query->execute();
return array_values($nids);
}
public function conditionalQuery() {
return [
'#title' => 'Published Nodes Called "ipsum lorem" That Have a Tag "test"',
'content' => [
'#theme' => 'item_list',
'#items' => $this->intermediateQuery()
]
];
}
protected function advancedQuery() {
$query = $this->entity_query->get('node')
->condition('status', 1)
->condition('changed', REQUEST_TIME, '<');
$group = $query->orConditionGroup()
->condition('title', 'ipsum lorem', 'CONTAINS')
->condition('field_tags.entity.name', 'test');
$nids = $query->condition($group)->execute();
return array_values($nids);
}
public function conditionalGroupQuery() {
return [
'#title' => 'Published Nodes That Are Called "ipsum lorem" Or Have a Tag "test"',
'content' => [
'#theme' => 'item_list',
'#items' => $this->advancedQuery()
]
];
}
下一步编辑既存的路由文件，调用公有方法：
query_example.simple:
path: 'examples/query_example/simple'
defaults:
_controller: '\Drupal\query_example\Controller\QueryExampleController::basicQuery'
requirements:
_access: 'TRUE'
query_example.intermediate:
path: 'examples/query_example/intermediate'
defaults:
_controller: '\Drupal\query_example\Controller\QueryExampleController::conditionalQuery'
requirements:
_access: 'TRUE'
query_example.advanced:
path: 'examples/query_example/advanced'
defaults:
_controller: '\Drupal\query_example\Controller\QueryExampleController::conditionalGroupQuery'
requirements:
_access: 'TRUE'