Define variables in template based on user being staff or not

I'm trying to display an HTML table of values with about 20 columns where say staff users see one subset of columns, and non-staff users see another subset of columns. I may want to define further types of users later. Now right now I have three static header rows so the template looks like

<table>
<tr>
  <th>Col A</th>
  {% if user.is_staff %}<th>Col B</th>{% endif %}
  ...
  {% if not user.is_staff %}<th>Col K</th>{% endif %}
</tr>
<tr>
  <td>Col A second header</td>
  {% if user.is_staff %}<td>Col B second header</td>{% endif %}
  ...
  {% if not user.is_staff %}<td>Col K second header</td>{% endif %}</tr>
<tr><td>Col A third header</td>  ...  </tr>

{% for obj in object_list %}
<tr>
  <td>{开发者_Go百科{ obj.col_a }}</td>
  {% if user.is_staff %}<td>{{ obj.col_b }}</td>{% endif %}
  ...
  {% if not user.is_staff %}<td>{{ obj.col_k }}</td>{% endif %}
</tr>
{% endfor %}</table>

However, I find non-DRY as every time, if I want to change if a user-type can see a column, I have to change it in 4 places. Or if I want to define multiple different classes of users, I'd have to have complicated if statements. I'd prefer something like

 {% if show_col_a %}<td>{{obj.col_a }}</td>{{% endif %}

Where I can define at the top of the template (or possibly in the view) that user.is_staff can see show_col_a. Is something like this possible? I'm using a generic view (object_list). Maybe modify all users to have attributes user.show_col_a somehow and do {% if user.show_col_a %}? I'm not sure how to add boolean attributes to users.

EDIT: May want multiple users with custom views (e.g., staff_view; admin_view, unprivileged, etc.), so if statements would get unwieldy. A cell's contents is typically more complicated than {{ obj.col_b }}; tried simplifying problem to get to the point. E.g.:

<td>{% if obj.custom_address %}
  {{ obj.custom_address.webprint|safe }}
{% else %}
  {{ obj.business.address.webprint|safe }}
{% endif %}</td>

Also while multiple templates would work with a simple switch like:

{% if user.is_staff %}
   {% include "template_staff.html" %}
{% else %}{% if user.is_admin %}
   {% include "template_admin.html" %}
{% else %}
   {% include "template_other.html" %}
{% endif %}
{% endif %}

I find its not DRY at all; e.g., every edit to a template has to be replicated in three template. I guess I could make a script that read generates the three templates from some super_template outside of django but its getting very inelegant.

This depends a lot on what view you have and templates.

Ways to do:

• make a public template and staff template and add a simple method to change the templates on the fly for the views.

• make a template tag:

  {% is_staff myvar %}

tag code:

class IsStaffNode(Node):
    def __init__(self, var):
        self.var = var

    def render(self, context):
        if context['user'].is_staff():
            return var.resolve(context)
        return ""


@register.tag
def is_staff(parser, token):
    var = parser.compile_filter(token.split_contents()[1])
    return IsStaffNode(var)

Homework: make it a block tag to include the td's so that it's shown either all or none.

{% isstaff myvar %}<td>{{ myvar }}</td>{% endisstaff %}

This way is more labor intensive than 2 different templates, but if you want to try, manipulating the context (or creating a separate context for the block only) might be useful.

• Make a context processor that would fill the context with some variables if the user is staff, or not if not.
• Make a tag that would include the template (inherit from IncludeNode) and manipulate the context.