如何在Django基本模板中呈现查询集? [英] How I do render a queryset in a Django base template?

问题描述

我有一个基本模板，该模板可以扩展到项目中几乎所有其他模板.我正在尝试使用数据库中的一些查询集填充类别导航栏，但是我的方法失败了.由于基本模板没有url，因此我发现很难渲染.这是我尝试过的:

I have a base template which extends to almost every other templates in my project. I am trying to populate my categories navigation bar with some queryset from my database but am failing with my approach. Since the base template has no url, I am finding it difficult to render. This is what I've tried:

这是我的视图功能

def base(request):
    categories = list(Category.objects.all())
    context = {
        'categories': categories
    }
    return render(request, 'ads/base.html', context)

这是我的html

{% for category in categories %}
    <div class="nav-item dropdown">
        <a href="#" class="nav-link dropdown-toggle" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
            { category.name }}&nbsp;
            <span class="float-right text-muted">
                <small>
                    <i class="fas fa-chevron-down"></i>
                </small>
            </span>
        </a>
    </div>
{% endfor %}

我只想用类别queryset填充导航栏

I just want to populate my navbar with the categories queryset

推荐答案

即使 base 视图具有URL，也不会有任何区别.URL触发一个视图，该视图呈现响应.模板与它没有(太多)关系.有时将模板用作生成此类响应的方法.但是它只能使用以某种方式传递的数据进行渲染.例如，通过该视图或模板标签，上下文处理器等.

Even if the base view had a URL, that would not make any difference. A URL triggers a view, and that view renders a response. A template has not (much) to do with it. A template is sometimes used as a way to generate such response. But it can only render with data that is passed somehow. For example through that view, or through template tags, context processors, etc.

例如，我们可以定义一个上下文处理器.在您的应用中，您可以在 context_processors.py 文件中定义一个函数:

We can for example define a context processor. In your app, you can define a function in the context_processors.py file:

# app/context_processors.py

def categories(request):
    from app.models import Category
    return {'categories': Category.objects.all()}

然后，您可以在 settings.py 中将该函数添加到上下文处理器中:

In the settings.py you can then add the function to the context processors:

# settings.py

# ...

TEMPLATES = [
    {
        'BACKEND': 'django.template.backends.django.DjangoTemplates',
        'DIRS': [],
        'APP_DIRS': True,
        'OPTIONS': {
            'context_processors': [
                'django.template.context_processors.debug',
                'django.template.context_processors.request',
                'django.contrib.auth.context_processors.auth',
                'django.contrib.messages.context_processors.messages',
                'app.context_processors.categories'
            ],
        },
    },
]

现在，每次渲染模板时，都将向映射到 Category.objects.all()查询集的上下文中添加 categories 变量. QuerySet 的计算是惰性的，因此，如果您不需要对其进行迭代，则不会在数据库上执行查询.

Now each time you render a template, you will add a categories variable to the context that is mapped on the Category.objects.all() queryset. QuerySets are evaluated lazily, so in case you do not need to iterate over it, the query is not performed on the database.

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