[FIXED] How to pass optional parameters to a view in Django?

Issue

I have a view that takes two optional keyword arguments: team and year_month

def monthly_data_list(request, year_month:str=None, team=None):

From the template, I want to call different combinations with either one of these 2 parameters, or both.

Django docs gives this example of implementing this:

path('monthly/list/', views.monthly_data_list, {'team':None, 'year_month'=None },name='monthly-data-list'),

However, calling this URL from the template with one or both arguments gives me a NoReverseMatch error:

hx-get="{% url 'drivers:monthly-data-list' team=None year_month=current_year_month %}"

I found a workaround suggested here, which is to define paths for all combinations of parameters. This works with 2 parameters, but gets complicated on more.

How do you correctly implement multiple optional parameters?

Solution

You misunderstand the documentation. If you write a path:

path(
    'monthly/list/',
    views.monthly_data_list,
    {'team': None, 'year_month': None},
    name='monthly-data-list',
),

that path will not take any parameters at all, optional or not. The path will accept /monthly/list/ as path, and it will fill in None for team and year_month.

Passing these parameters is often done if your view can be served through multiple patterns, like:

urlpatterns = [
    path(
        'monthly/list/',
        views.monthly_data_list,
        {'team': None, 'year_month': None},
        name='monthly-data-list',
    ),
    path(
        'monthly/list/<str:team>/',
        views.monthly_data_list,
        {'year_month': None},
        name='monthly-data-list',
    ),
    path(
        'monthly/list/<str:team>/<str:year_month>/',
        views.monthly_data_list,
        name='monthly-data-list',
    ),
]

so now we have three patterns, one without any team or year_month, and then we use None instead, one with /<str:team>/, in which case we will fill in None for `year_month, and finally one where one can specify both.

In that canse we thus can make a reverse by mentioning the parameters necessary, so int his case for example:

{% url 'monthly-data-list' team='Foo' %}

this will then pick the second path, and fill in 'Foo' for the team, and it will call the monthly_data_list with None for year_month.

Answered By - willeM_ Van Onsem