Django Lineage

Which navigation element is "active" in a template? Lineage determines a navigation element's state by inspecting the page URL:

{% load lineage %}

<ul>
    <li class="{% ancestor '/home/' %}"><a href="/home/">Home</a></li>
    <li class="{% ancestor '/blog/' %}"><a href="/blog/">Blog</a></li>
    <li class="{% ancestor '/about/' %}"><a href="/about/">About</a></li>
</ul>

If the argument of ancestor matches the start of the URL (e.g. this nav element is at least a parent of this page), it outputs "active". It's that simple!

Installation

Install using pip:

pip install django-lineage

Add 'lineage' to INSTALLED_APPS in settings.py:

INSTALLED_APPS = (
    'lineage',
)

Usage

The ancestor tag needs to, of course, be loaded into your template:

{% load lineage %}

The first way to use Lineage is the aformentioned ancestor tag. Again if the argument matches the start of the page URL it outputs "active", this should handle most use cases:

{% ancestor '/arbitrary/path/' %}

ancestor can also handle variables, filters and all that stuff:

{% ancestor some_variable|somefilter %}

Most importantly it also accepts url tag type reverse resolution (Behind the scenes the url tag derives our expected argument - a URL path string.)

{% ancestor 'core:model_detail' model.pk %}

Output Defaults to "active"

By default ancestor outputs "active" on a match. You can alter this default by adding LINEAGE_ANCESTOR_PHRASE = 'newphrase' to settings.py

Overring Output

Override output on demand using the ifancestor/endifancestor combo:

{% ifancestor 'pattern_name' %}
    This text here is only renderd if the
    URL argument is an ancestor.
{% endifancestor %}

Assumptions

Lineage depends on sensible URL hierarchies, because it compares paths using regex matching. {% ancestor '/base/' %} will fire if the current URL begins with /base/. For example /base/ and /base/section/page/ return true, but /other/path/ and /base (missing trailing slash) will not.

request must be present in the request context, since it's used to determine the current URL. Django has a context preprocessor that can insert it for you.

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