如何限制 django 视图内的 get_next_by_FOO ？包含代码

Question

我在视图中使用了 get_next_by_FOO 来显示一组记录中下一项的绝对 url，但是当它到达查询集末尾时，会引发错误。

如何阻止我的视图引发此错误，而只是输出一些 html 让我知道它已经到达集合的末尾？

非常感谢所有帮助。

这是错误消息、我的视图和模板代码。

错误

    Exception Type:     DoesNotExist
    Exception Value:    Body matching query does not exist.

视图

def news_view(request, url):
news = get_object_or_404(Body, url=url)
next = news.get_next_by_published()
pre = news.get_previous_by_published()
return render_to_response('news/news_view.html', {
    'news': news,
    'pre': pre,
    'next': next
}, context_instance=RequestContext(request))

模板

    <a href="{{ next.get_absolute_url }}">Next News</a></p>
    <a href="{{ pre.get_absolute_url }}">Previous News</a></p>

Answer 1

蛮力答案是：

def news_view(request, url):
    news = get_object_or_404(Body, url=url)
    try:
        next = news.get_next_by_published()
    except Body.DoesNotExist:
        next = None
    try:
        pre = news.get_previous_by_published()
    except Body.DoesNotExist:
        pre = None
    return render_to_response('news/news_view.html', {
        'news': news,
        'pre': pre,
        'next': next
        }, context_instance=RequestContext(request))

模板：

{% if next %}<a href="{{ next.get_absolute_url }}">Next News</a></p>{% else %}<span class="disabled">At Last Item</span>{% endif %}
{% if pre %}<a href="{{ pre.get_absolute_url }}">Previous News</a></p>{% else %}<span class="disabled">At First Item</span>{% endif %}

Answer 2

我这样做：

def news_view(request, url):
    news = get_object_or_404(Body, url=url)
    return direct_to_template(request, 'news/news_view.html', {'news': news,})

模板：

{% with news.get_previous_by_pub_date as prev %}
   {% if prev %}
       <a class="left btn" href="{{ prev.get_absolute_url }}">Previous News</a>
   {% endif %}
{% endwith %}
{% with news.get_next_by_pub_date as next %}
    {% if next %}
        <a class="right btn" href="{{ next.get_absolute_url }}">Next News</a>
    {% endif %}
{% endwith %}