如何在django模板中访问字典元素？ [英] how to access dictionary element in django template?

问题描述

我有这个代码在模板中，我想打印出每个选择的票数。投票只是字典，而选择是模型对象。

  {％在选择中选择％} 
 {{choice。 choice}}  -  {{votes [choice.id]}}< br /> 
 {％endfor％} 
  

它引发了一个异常，此消息无法解析余数

解决方案

为了回应/扩展Jeff的评论，我认为你应该瞄准的只是你的Choice课程中的一个属性它计算与该对象相关联的投票数：

  class Choice（models.Model）：
 text = models .CharField（max_length = 200）
 
 def calculateVotes（self）：
 return Vote.objects.filter（choice = self）.count（）
 
 vote =财产（calculateVotes）
  

然后在您的模板中，您可以执行以下操作：

  {％在选择中选择％} 
 {{choice.choice}}  -  {{choice.votes}}< br /> 
 {％endfor％} 
  

模板标签是IMHO对此解决方案有点过分，但它也不是一个可怕的解决方案。 Django中的模板的目标是将您与模板中的代码隔离开，反之亦然。

我会尝试上面的方法，看看ORM产生的SQL是什么，因为我不确定我的头顶，如果它会预先缓存属性，只需为该属性创建一个子选择，或者它将迭代/点播运行查询来计算投票数。但是，如果它产生残酷的查询，您可以随时使用自己收集的数据填充视图中的属性。

I have this code in template, which I would like to printout number of votes that each choice got. votes is just dictionary while choices are model object.

{% for choice in choices %}
    {{choice.choice}} - {{votes[choice.id]}} <br />
{% endfor %}

it raises an exception with this message "Could not parse the remainder"

解决方案

To echo / extend upon Jeff's comment, what I think you should aim for is simply a property in your Choice class that calculates the number of votes associated with that object:

    class Choice(models.Model):
        text = models.CharField(max_length=200) 

        def calculateVotes(self):
            return Vote.objects.filter(choice = self).count()

        votes = property(calculateVotes)

And then in your template, you can do:

    {% for choice in choices %}
            {{choice.choice}} - {{choice.votes}} <br />
    {% endfor %}

The template tag, is IMHO a bit overkill for this solution, but it's not a terrible solution either. The goal of templates in Django is to insulate you from code in your templates and vice-versa.

I'd try the above method and see what SQL the ORM generates as I'm not sure off the top of my head if it will pre-cache the properties and just create a subselect for the property or if it will iteratively / on-demand run the query to calculate vote count. But if it generates atrocious queries, you could always populate the property in your view with data you've collected yourself.

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