Symfony/Twig中展示ManyToOne关联实体属性的正确姿势

// src/Entity/Cats.php

use Doctrine\Common\Collections\ArrayCollection;
use Doctrine\Common\Collections\Collection;
use Doctrine\ORM\Mapping as ORM;

/**
 * @ORM\Entity(repositoryClass=CatsRepository::class)
 */
class Cats
{
    // ... 其他属性和方法

    /**
     * @ORM\OneToMany(targetEntity=Appointment::class, mappedBy="cat", orphanRemoval=true)
     */
    private $appointments;

    public function __construct()
    {
        $this->appointments = new ArrayCollection();
    }

    /**
     * @return Collection|Appointment[]
     */
    public function getAppointments(): Collection
    {
        return $this->appointments;
    }

    // ... addAppointment, removeAppointment 等方法
}

// src/Entity/Appointment.php

use Doctrine\ORM\Mapping as ORM;

/**
 * @ORM\Entity(repositoryClass=AppointmentRepository::class)
 */
class Appointment
{
    // ... 其他属性和方法

    /**
     * @ORM\ManyToOne(targetEntity=Cats::class, inversedBy="appointments", cascade={"persist"} )
     * @ORM\JoinColumn(nullable=false)
     */
    private $cat; // 注意这里是单数 'cat'

    public function getCat(): ?Cats
    {
        return $this->cat;
    }

    public function setCat(?Cats $cat): self
    {
        $this->cat = $cat;

        return $this;
    }
}

{# 错误的尝试 #}
{% extends 'base.html.twig' %}
{% block title %}Appointment{% endblock %}
{% block main %}

<h1>Appointment Details</h1>

{# 错误示范：尝试遍历不存在的 'appointment.cats' 集合 #}
{% for cat in appointment.cats %}
    <div>
        {# 错误示范：直接访问 'appointment.cat_id'，而实体通常通过对象访问属性 #}
        <td>{{ appointment.cat_id }}</td>
    </div>
{% endfor %}

{% endblock %}

Neither the property "cats" nor one of the methods "cats()", "getcats()"/"iscats()"/"hascats()" or "__call()" exist and have public access in class "App\Entity\Appointment".

{# 正确的访问方式 #}
{% extends 'base.html.twig' %}
{% block title %}Appointment List{% endblock %}
{% block main %}

<h1>Appointments Overview</h1>

{# 假设 'appointments' 是一个包含 Appointment 对象的集合 #}
{% for appointment in appointments %}
    <div>
        {# 直接通过 'appointment.cat' 获取关联的 Cat 对象 #}
        {% set cat = appointment.cat %}

        {# 然后访问 Cat 对象的属性，例如 ID #}
        <p>Appointment ID: {{ appointment.id }} - Associated Cat ID: {{ cat.id }}</p>
        {# 如果 Cat 实体有 'name' 属性，也可以这样访问： #}
        {# <p>Associated Cat Name: {{ cat.name }}</p> #}
    </div>
{% else %}
    <p>No appointments found.</p>
{% endfor %}

{# 如果你正在显示单个 Appointment 对象的详情页 #}
{% if appointment is defined and appointment.cat is defined %}
    <h2>Details for Appointment #{{ appointment.id }}</h2>
    <p>Associated Cat ID: {{ appointment.cat.id }}</p>
    {# 同样可以直接访问其他属性，例如： #}
    {# <p>Associated Cat Name: {{ appointment.cat.name }}</p> #}
{% endif %}

{% endblock %}