无法访问空变量的属性（“用户”）答案

【问题标题】：Impossible to access an attribute ("user") on a null variable无法访问空变量的属性（“用户”）
【发布时间】：2017-12-02 17:23:48
【问题描述】：

我收到此错误，无法弄清楚如何解决它。这个想法是列出用户的所有书籍。使用用户 ID 调用时的路径可以正常工作，例如：userbooks/4。但使用用户名 userbooks/paul 调用我收到此错误“无法访问空变量上的属性（“用户”）。”

   <h2 > <a href="{{ path('userbooks',{'user' : entry.user}) }} ">{{ entry.title | title }}</a></h2>

查看用户手册操作：

  public function viewuserbooksAction($user)
{
    $em = $this->getDoctrine()->getManager();

    $book = $em->getRepository('BookReviewBookBundle:Book')->find($user);

    return $this->render('@BookReviewBook/Book/viewuserbooks.html.twig',
        ['book' => $book]);

}

viewuserbook.html.twig

{% extends '@BookReviewBook/layout.html.twig' %}
{% block title %}{% endblock %}
{% block body %}

  {% for book in book.user.entries %}
  <h1>{{ book.title }} </h1>
<div>
<img class="img-valign" src="{{ asset('images/book/'~ book.path )  }}" , style 
 = "width:300px;height:300px;" class="img-thumbnail " />
<span class="text2">{{ book.author }}</span>

{{ book.averageRating |rating }}
</div>
<hr class="style4">
<p>{{ book.summary|nl2br }} </p>
<p><small>Posted by {{ book.user }} on {{ book.timestamp|date('H:i d/m/y') }}
</small>
 </p>
<hr class="style4">

{% endfor %}

routing.yml

 userbooks:
     path: /userbooks/{user}
     defaults: { _controller: BookReviewBookBundle:User:viewuserbooks }

  view:
     path: /view/{id}
     defaults: { _controller: BookReviewBookBundle:Book:view }
     requirements:
       id: \d+

【问题讨论】：

这可能是因为您的图书实体通过 ID 而不是用户名与用户建立了连接。
您的代码 sn-p 中有很多 user 变量。导致此错误的确切原因在哪里？
@DonCallisto 此路径 {{ path('userbooks',{'user' : entry.user}) }} 指向用户名变量。是否可以将其更改为指向用户 ID？
是的，只需输入entry.id 而不是entry.user
什么条目？您没有任何入口变量。只需在渲染控制器的方法中传递它

标签： php symfony doctrine entity

【解决方案1】：

感谢大家的回复和帮助。现在完美运行。必须通过用户名查找

查看用户手册操作：

public function viewuserbooksAction($username)
{
    $em = $this->getDoctrine()->getManager();

    $book = $em->getRepository('UserBundle:User')->find($username);

    return $this->render('@BookReviewBook/Book/viewuserbooks.html.twig',
        ['user' => $book]);

}

viewuserbook.html.twig

 {% extends '@BookReviewBook/layout.html.twig' %}
 {% block title %}{% endblock %}


 {% block body %}


 {% for book in user.entries %}
 <h1>{{ book.title }} </h1>
 <div>
 <img class="img-valign" src="{{ asset('images/book/'~ book.path )  }}" , 
   style 
   = "width:300px;height:300px;" class="img-thumbnail " />
 <span class="text2">{{ book.author }}</span>

  {{ book.averageRating |rating }}
  </div>
  <hr class="style4">
   <p>{{ book.summary|nl2br }} </p>
    <p><small>Posted by {{ book.user }} on {{ book.timestamp|date('H:i d/m/y') 
   }}
   </small>
   </p>

  {% endfor %}

  {% endblock %}

routing.yml

userbooks:
     path: /userbooks/{username}
     defaults: { _controller: BookReviewBookBundle:User:viewuserbooks }

index.html.twig

  <h2 > <a href="{{ path('userbooks',{ username : entry.user.id}) }} ">{{ 
  entry.title | title }}</a></h2>

【讨论】：