symfony 3多对多的双向超延迟关联

Question

我有两个实体广告1城市

一个广告属于许多城市
一个城市有很多广告

我需要一个解决方案来关联这两个实体，我的目标是：

从$ advert对象获取$ cities
从$ city获取$ adss

$ advert-＆GT; getCities（）
$都市＆GT; getAdverts（）

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<?php

namespace Ligo\PlatformBundle\Entity;

use Doctrine\ORM\Mapping as ORM;
use Gedmo\Mapping\Annotation as Gedmo;
use Doctrine\ORM\Mapping\ManyToMany;

/**
 * Advert
 *
 * @ORM\Table(name="advert")
 * @ORM\Entity(repositoryClass="Ligo\PlatformBundle\Repository\AdvertRepository")
 */
class Advert
{
     /**
     * @ORM\ManyToMany(targetEntity="City")
     * @ORM\JoinTable(name="adverts_cities",
     *      joinColumns={@ORM\JoinColumn(name="advert_id", referencedColumnName="id")},
     *      inverseJoinColumns={@ORM\JoinColumn(name="city_id", referencedColumnName="id")}
     *      )
     */
    private $Cities;

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<?php

namespace Ligo\PlatformBundle\Entity;

use Doctrine\ORM\Mapping as ORM;

/**
 * City
 *
 * @ORM\Table(name="city")
 * @ORM\Entity(repositoryClass="Ligo\PlatformBundle\Repository\CityRepository")
 */
class City
{
    /**
    * @ORM\ManyToMany(targetEntity="Advert", mappedBy="Cities")
    **/
    private $Adverts;

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