Question

I’m looking to set a default behavior in a template to be included.

I have a problem with Django template system not allowing to set variables in template (I’ve read about the Django Philosophy, and I understand it).

Here is my example problem:

1. I want to include a template to render a newsfeed:

   template.html:
   ...
   {% include "_newsfeed.html" with slicing=":20" %}
   ...
   

   I would like to not be forced to enter the slicing argument, and set a default behavior, let’s say ":20"

2. In my _newsfeed.html , I would like to do (pseudo-code, it doesn’t work):

   _newsfeed.html:
   ...
   {% if not slicing %}{% with slicing=":20" %}{% endif %}
   
   {% for content in newsfeed_content|slice:slicing %} 
       {# Display content #}
   {% endfor %}
   
   {% if not slicing %}{% endwith %}{% endif %}
   

Instead, I end up doing this below, that doesn’t follow the DRY rule (and doesn’t satisfy me!):

_newsfeed.html:
...
{% if not slicing %}{% with slicing=":20" %}

    {% for content in newsfeed_content|slice:slicing %} 
        {# Display content #}
    {% endfor %}

{% endwith %}{% else %}

    {% for content in newsfeed_content|slice:slicing %} 
        {# Display content #}
    {% endfor %}

{% endif %}

How should I do ?

Answer 1

If you want to do this via your template not your views file, you could create your own filter based on slice e.g.

from django.template.defaultfilters import slice_filter

@register.filter("slice_default", is_safe=True)
def slice_filter_20(value, arg=":20"):
    return slice_filter(value, arg)