如何在Django模板中打破“for循环”

I have this code

我有这段代码

    {% for account in object_list %}
        <tr>
        {% for field, value in book.get_fields %}
              <th>{{ field.verbose_name }}</th> 
        {% endfor %}
        </tr>
    {{ break }}
    {% endfor %}

I want to break the for loop after first iteration. break is not working

我想在第一次迭代之后打破for循环。休息不工作

5 个解决方案

#1

There is no break in Django template system. Django template system is not programmed with python but with its own language.

Django模板系统没有中断。Django模板系统不是用python编程的，而是用它自己的语言编写的。

Depending on what you need to do, you might find this question useful. Otherwise, just put the one and only account you are trying to print on HTML on a special field on your RequestContext.

根据你需要做什么，你可能会发现这个问题很有用。否则，只需将要在HTML上打印的唯一帐户放在RequestContext的一个特殊字段上。

#2

I think you should use slice to achieve your goal

我认为你应该用slice来实现你的目标。

{% for account in object_list|slice:":1" %}

#3

You can't use break statement but you can choose not to print them on html. It's not a best solution but you can use it. I use the following one;

不能使用break语句，但可以选择不在html上打印它们。这不是最好的解决方案，但你可以使用它。我用下面这个;

{%for tumbnail in image %}
         {%if tumbnail.object_id == element.id %}
          <img src="/media/{{ tumbnail.image }}" class="tr_all_hover"alt="">

{{ "<!--" }}
  {%endif%} 
{%endfor%}     
{{ "-->" }}

Its basicly seem like this on browser. http://i.stack.imgur.com/MPbR3.jpg

在浏览器上它的基本原理是这样的。http://i.stack.imgur.com/MPbR3.jpg

#4

I found a way to do this with a condition. It's ugly and hacky, but it works (for me). first is what the OP wanted, but this answers the actual question more closely.

我找到了一种方法来解决这个问题。它既丑陋又陈腐，但(对我来说)很管用。首先是OP想要什么，但这更接近实际问题。

Given this:

鉴于这种:

obj = {
  'children': [
    { 'possessions' : { 'toys': [] } },
    { 'possessions' : { 'toys': ['train'] } }
    { 'possessions' : { 'toys': ['train', 'ball'] } }
  ]
}

I wanted to know if my obj has any children with possessions that are toys.

我想知道我的孩子是否有玩具。

Here's what I did:

Python Equivalent:

if ([child for child in obj.children if child.possessions.toys]):
  # Whatever

Django Template:

My approach was to use regroup to build sets of candidates which did or didn't match the criteria:

我的方法是使用regroup建立一组符合或不符合标准的候选人:

{% regroup obj.children by possessions.toys|length_is:"0" as by_toys %}
{% for check in by_toys %}{% if check.grouper == False %}
  Whatever
{% endif %}{% endfor %}

regroup builds a new object that is essentially:

regroup构建的新对象本质上是:

[
  { 'grouper': '', 'list': [/*...*/] },
  { 'grouper': True, 'list': [/*...*/] },
  { 'grouper': False, 'list': [/*...*/] }
]

The length_is:"0" makes sure that we have at most three elements in that list and the grouper is either True or False or ''. Then we iterate over the list and check for a False value.

length_is:“0”确保我们在列表中最多有3个元素，grouper要么是True，要么是False。然后遍历列表并检查错误值。

• If there are no children it'd be an empty list and the if would never be hit.
• 如果没有孩子，它将是一个空列表，如果永远不会被击中。
• If no children have toys, it'd be a list without a False grouper.
• 如果没有孩子有玩具，那就没有假的石斑鱼。
• If all children have toys, it'd be a list with a False grouper.
• 如果所有的孩子都有玩具，那就是一张假石斑鱼的清单。
• If some children have toys, it'd be a list with False and True groupers.
• 如果有些孩子有玩具，那就会是一个有假的和真的石斑鱼的清单。

#5

You can use your Django template system for loop in javascript for loop as inner loop and can use break as follows :-

您可以使用您的Django模板系统for循环在javascript for循环中作为内部循环，并可以使用break如下:-

for(var i=0;i<1;i++){
        {% for owner in Owner %}
            id  = "{{owner.id}}";
            if(id == pk1){
                f="{{owner.flat}}";
                break;
            }             
        {% endfor %}
     }