php - Twig "is defined"是否适用于可迭代对象？

Question

我有一个模板，它总是接收一个可迭代对象，所以我可以迭代它。在循环中，每个“结果”中的对象可能具有也可能不具有显示图像所需的属性，因此我一直在尝试使用“已定义”:。例如:

{% for result in results %}
    {% if result.thumbnail is defined %}
    <img src='{{ result.thumbnail }}' >
    {% endif %}
{% endfor %}

但是当我运行它时，我总是从 Twig 得到同样的错误:

Method 'thumbnail' is not implemented

我认为“已定义”方法会为我解决这个问题。我错过了什么？

我正在使用 Twig (1.18) 和 Silex (~1.2)。

谢谢你，拉塞尔

更新

这是当迭代器中有两个对象时 {{ dump(result) }} 的输出:

object(Turtle\Model\Attachment)[1056]
  protected 'datatype' => string 'Attachments' (length=11)
  protected 'filename' => string '560166.jpg' (length=10)
  protected 'displayname' => null
  protected 'description' => null
  protected 'collection' => string 'product' (length=7)
  protected 'width' => int 360
  protected 'height' => int 360
  protected 'file' => string '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'... (length=34432)
  protected 'mimetype' => string 'image/jpeg' (length=10)
  protected 'subdir' => string 'products/acme' (length=16)
  protected 'admupdated' => null
  protected 'website' => string 'gaspares' (length=8)
  protected 'contentids' => null
  protected 'category' => null
  protected 'id' => string 'pIPp0QP_TYqA0JuWmPGBmw' (length=22)
  protected 'app' => null
  protected 'entity' => null
  protected 'item' => null
  protected 'namefield' => string 'filename' (length=8)
  protected 'filterfield' => null
  protected 'progress' => 
    array (size=0)
      empty
  public 'checksum' => string 'c3d3f0194b988297e603367d5fd3837b' (length=32)

object(Turtle\Model\Product)[1055]
  protected 'datatype' => string 'Products' (length=8)
  protected 'state' => null
  protected 'manufacturer' => string '****' (length=7)
  protected 'code' => string '560166' (length=6)
  protected 'ghost' => boolean false
  protected 'discontinued' => boolean false
  protected 'title' => string '****' (length=39)
  protected 'summary' => string '****' (length=43)
  protected 'description' => string '****' (length=407)
  protected 'information' => string '****' (length=257)
  protected 'delivery' => string 'Next Working Day, On A' (length=22)
  protected 'delivery_type' => string 'On A UPS Before 12.30 Service' (length=29)
  protected 'tagname' => null
  protected 'tag' => 
    array (size=7)
      0 => string 'AR4' (length=3)
      1 => string 'AR3' (length=3)
      2 => string 'AR2' (length=3)
      3 => string 'AR5 ' (length=4)
      4 => string 'AR7' (length=3)
      5 => string 'AR6' (length=3)
      6 => string 'AR1' (length=3)
  protected 'warranty' => string '1 Year' (length=6)
  protected 'catid' => null
  protected 'cost' => string '74.46' (length=5)
  protected 'price' => null
  protected 'image' => string 'products/acme/560166.jpg' (length=27)
  protected 'thumbnail' => string 'products/acme/thumb560166.jpg' (length=32)
  protected 'techinfo' => string 'notechinfo.jpg' (length=14)
  protected 'checksum' => string '4db345d582ac77dcd5594dc75bc2726d' (length=32)
  protected 'lastmodified' => int 1424208468
  protected 'admupdated' => null
  protected 'id' => string 'IF8B94PuRieIsHWARfI51w' (length=22)
  protected 'app' => null
  protected 'entity' => null
  protected 'item' => null
  protected 'namefield' => string 'code' (length=4)
  protected 'filterfield' => null
  protected 'progress' => 
    array (size=0)
      empty

可以看出，第一个对象没有“缩略图”，但第二个对象有。 Twig 在第一个上爆炸了。

更新 2

为了提供更完整的图片，我现在运行的代码具有更新的语法，如@prisoner 所建议的:

{% for result in results %}
<div class='row'>
  <div class='col-md-1 col-md-offset-1'>
    {% if result.thumbnail is defined and result.thumbnail is not empty %}
    <a href="{{ app.url_generator.generate('product_show', {'id': result.id}) }}">
      <img src='/images/{{ result.thumbnail }}' align='left' height='75'>
    </a>
    {% endif %}
  </div>
</div>
{% endfor %}

不幸的是，这并没有解决问题，我得到了和以前一样的错误。这次是完整的:

Twig_Error_Runtime: An exception has been thrown during the rendering of a template ("Method 'thumbnail' not implemented") in "search_results" at line 4. (uncaught exception) at /usr/local/turtle/lib/vendor/twig/twig/lib/Twig/Template.php line 304 {"exception":"[object] (Twig_Error_Runtime: An exception has been thrown during the rendering of a template (\"Method 'thumbnail' not implemented\") in \"search_results\" at line 4. at /usr/local/turtle/lib/vendor/twig/twig/lib/Twig/Template.php:304

我原以为'defined'会检查属性是否存在，可能使用property_exists之类的，这样在检查时就不会抛出错误。

更新 3

我向两位评论者@prisoner 和@Alan Tiemblo 道歉，我确实有神奇的 setter 方法。我忘记了在迭代器中设置的两个类都扩展了一个“模型”类，其中包含 __get 和 __set 方法。

这会影响我所看到的吗？是否出于某种原因，Twig 无法使用父类？

Answer 1

为了处理这种情况，我习惯使用 default过滤器:

{% if result.thumbnail|default('') != '' %}
  {# ... #}
{% endif %}

编辑:

Twig 的属性访问器看不到魔法 getter(参见 \Twig_Template::getAttribute 方法)。

相反，随便调用你的 magic getter:

{% if result.__get('thumbnail')|default('') != '' %}
  {# ... #}
{% endif %}