Django模板if语句总是计算为true [英] Django template if statement always evaluates to true
问题描述
这看起来应该很简单，但由于某种原因我无法解决这个问题。我正在使用Django 1.4。我试图在模板渲染过程中进行基本检查以查看列表 QuerySet是否为空，但我正在使用的if语句似乎总是评估为true。
This seems like it should be pretty straightforward, but for some reason I am unable to solve this problem. I'm using Django 1.4. I am trying to do a basic check to see if a list QuerySet is empty or not during template rendering, but the if statement I'm using seems always to evaluate to true.
我有一个Django模板，内容如下：
I have a Django template that reads:
{% extends 'includes/base.html' %}
{% if object_list %}
...
{% block data %}
{% for object in object_list %}
...
{{ object.create_date }}
...
{% endfor %}
{% endblock data %}
...
{% endif %}
'base.html'有块：
'base.html' has the block:
<body>
{% block content %}
...
<div class="row-fluid">
<div class="span12">
{% block data %}
<div align="center"><i>No data.</i></div>
{% endblock data %}
</div><!-- span12 -->
</div><!-- row -->
{% endblock content %}
...
</body>
生成QuerySet的视图函数在这里：
The view function generating the QuerySet is here:
def barcode_track(request, model):
query = request.GET.get('barcode_search', '')
object_list = model.objects.all()
if query:
object_list = model.objects.filter(barcode__icontains=query)
return render_to_response('barcode_track/barcode_list.html',
{'object_list': object_list, 'query': query},
context_instance=RequestContext(request))
这是通过此表单调用：
<form id="barcode_search_form" method="get" action="" class="form">
<input type="text" name="barcode_search" value="{{ query }}" />
<button type="submit" class="btn">Search</button>
</form>
和urls.py行：
urlpatterns = patterns('barcode_track.views',
url(r'^$', 'barcode_track', {'model': Barcode},
name="barcode_track"),)
这个想法是只有在<$存在于<$时才会显示结果c $ c> object_list ，否则父块将保持不变。我尝试更改 object_list 的名称，并在页面上打印 {{dicts}} 以确保 object_list 实际上是空的（它是）。我没有使用通用视图，虽然我意识到这个名字的含义也是如此。实际上我在使用类似逻辑编写的其他应用程序中遇到了这个问题，所以我必须系统地做错误的事情。
The idea is that results will only be presented if they exist in object_list, and otherwise the parent block will remain unaltered. I have tried changing the name of object_list, and I have printed {{ dicts }} to the page to ensure that object_list is, in fact, empty (which it is). I am not using a generic view, although I realize that the name suggests as much. I have actually had this trouble in a different app I wrote using similar logic, so I must be doing something systematically incorrectly.
我在这里缺少什么？
推荐答案
你不能将之类的控制流标签包装在附近块。您的问题是，子模板的块数据的定义正在被使用，因为它就在那里。
You can't wrap control flow tags like if around a block. Your problem is that the child template's definition for block data is being used simply because it's there.
你可以修复它通过在块数据中放置 if 标记。如果要在列表为空时继承父级内容，请添加 else 大小写扩展为 {{block.super}} 。
You can fix it by placing the if tag inside block data. If you want to inherit the parent's contents when the list is empty, add an else case that expands to {{ block.super }}.
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