Django dynamic urls with multiple arguments

Question

I am somewhat new to Django and I figured I would start of by building a standard library app.

What I had initialy created was a url pattern using slugs that shows you all the articles in a journal via http://127.0.0.1:8000/Albums/[album name]/.

This worked. What I then tried to do was make the article names clickable so that they would refer you to a page containing details about the song. Particularly I wanted these details to be accessible via a link of the form http://127.0.0.1:8000/Albums/[article name]/[article_id]/. Where article_id at the moment is the primary key in a database table containing all articles.

In order to do so I defined two url patterns:

urlpatterns = [
    url(r'^(?P<slug_journal>[\w-]+)/$', views.Journal_Article_Page, name='Journal_Page'),
    url(r'^(?P<slug_journal>[\w-]+)/(?P<id>\d+)/$', views.Journal_Article_Page, name='Journal_Article_Page'),
]

and a view:

def Journal_Article_Page(request, slug_journal=None, id=None):
    if slug_journal:
        if id:
            farticle = get_object_or_404(Article_Draft_Table_1, DRAFT_ID = id)
            return render(request, 'journal_article_details.html', { 'farticle': farticle, 'fjournal': slug_journal })
        else:
            fjournal = get_object_or_404(Journal_Table, Journal_slug = slug_journal).JOURNAL_ID
            articles = Article_Draft_Table_1.objects.filter(JOURNAL_ID = fjournal)
            return render(request, 'journal_articles.html', { 'articles': articles })

And finally a template:

{% extends 'base.html' %}

{% block content %}

    <p>List of articles.</p>

    <br>

    {% for article in articles %}
        <div class="col-sm-10">
        <a href='{% url "Journal_Article_Page" slug_journal=fjournal id=article.DRAFT_ID %}'>{{ article.Draft_title }}</a>
        </div>
    {% endfor %}

{% endblock %}

I then end up with thw following error:

Reverse for 'Journal_Article_Page' with arguments '()' and keyword arguments '{'id': 3, 'slug_journal': ''}' not found. 1 pattern(s) tried: ['Journals/(?P<slug_journal>[\\w-]+)/(?P<id>\\d+)/$']

Which to my appears to imply that the slug_journal string is not passed on correctly. In fact if I swap out fjournal in the template with the actual string of a particular journal name everything does work. I have now tried a number of different ways to solve this problem but can't seem to find a solution. I am in fact not even sure if the value is not passed on or whether I am not refering to it correctly in the template. Any help would be appreciated!

You're not passing fjournal variable to the context dict. This dict {'articles': articles} only has the articles variable in it. Add the fjournal argument to it as well. — xyres
– xyres, Commented Nov 27, 2016 at 16:21
That part corresponds to the list, I think there should be only one argument there no? Or does it somehow mess with the other option of the if statement? — DisneylandSC
– DisneylandSC, Commented Nov 27, 2016 at 18:19
Did you try adding fjournal adding to that context dict? And no, there shouldn't be just one variable there. You can add as many as you want. — xyres
– xyres, Commented Nov 27, 2016 at 19:17
My bad, you are correct. I had just completely misunderstood what you were pointing to. This did indeed solve my problem. Thanks a million! — DisneylandSC
– DisneylandSC, Commented Nov 28, 2016 at 14:56

Håken Lid · Accepted Answer · 2016-11-27 19:24:52Z

3

You have not included a fjournal value in the context, so the template engine will just use an empty string. The pattern expects at least one character in the slug [\w-]+ so the empty slug string will not match any url pattern.

You must include fjournal into the context dictionary. Something like this should probably work.

return render(request, 'journal_articles.html', 
              {'articles': articles, 'fjournal': slug_journal})

In addition, your code will be easier to read and maintain if you split the article list and the article itself into two different view functions instead of using Journal_Article_Page for both.

It's also convention to use only lower case letters in function names. So you could call the functions article_page and journal_article_list or something like that.

answered Nov 27, 2016 at 19:24

Håken Lid

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2 Comments

DisneylandSC Over a year ago

This solved my problem! thanks. Could you perhaps say something more about why turning this into two seperate views would be better according to you?

Håken Lid Over a year ago

It's a subjective opinion. Code that is clear and explicit is easier to maintain and debug. One url route -> one view function. Simple is better than complicated. Flat is better than nested. Readability counts. python.org/dev/peps/pep-0020

neverwalkaloner · Accepted Answer · 2016-11-27 16:17:32Z

1

Django tries each patterns in urlpatterns and returns first which corresponds to request. I believe just swap urls in urlpatterns will help:

urlpatterns = [    
url(r'^(?P<slug_journal>[\w-]+)/(?P<id>\d+)/$', views.Journal_Article_Page, name='Journal_Article_Page'),
url(r'^(?P<slug_journal>[\w-]+)/$', views.Journal_Article_Page, name='Journal_Page'),
]

answered Nov 27, 2016 at 16:17

neverwalkaloner

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2 Comments

DisneylandSC Over a year ago

Thanks for the response. I tried swapping the url patterns, sadly it gave me the exact same error.

neverwalkaloner Over a year ago

@DisneylandSC seems like you also should add fjournal value into context as Haken Lid said in his answer and swap urls.

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