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

问题描述

我想打印出每个选择获得的票数。我在模板中有以下代码：

I would like to print out the number of votes that each choice got. I have this code in a template:

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

投票只是字典，而选择是模型对象。

votes is just a dictionary while choices is a model object.

此消息引发异常：

"Could not parse the remainder"

推荐答案

要回应/扩展Jeff的评论，我认为您应该针对的只是Choice类中的一个属性，计算与该对象关联的投票数：

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)

然后在模板中，您可以执行以下操作：

And then in your template, you can do:

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

模板标签，恕我直言，对于该解决方案来说有点过头了，但不是一个可怕的解决方案。 Django中模板的目标是使您与模板中的代码隔离，反之亦然。

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.

我会尝试上述方法，看看ORM生成的SQL不是我生成的确保它会预先缓存属性并为该属性创建一个子选择，还是会迭代/按需运行查询以计算投票数，这是我的头上问题。但是，如果它产生了残酷的查询，您总是可以使用自己收集的数据填充视图中的属性。

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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