How to implement breadcrumbs in a Django template?
My view functions emit the breadcrumbs as a simple list.
Some information is kept in the user's session. Indirectly, however, it comes from the URL's.
Breadcrumbs are not a simple linear list of where they've been -- that's what browser history is for. A simple list of where they've been doesn't make a good breadcrumb trail because it doesn't reflect any meaning.
For most of our view functions, the navigation is pretty fixed, and based on template/view/URL design. In our cases, there's a lot of drilling into details, and the breadcrumbs reflect that narrowing -- we have a "realm", a "list", a "parent" and a "child". They form a simple hierarchy from general to specific.
In most cases, a well-defined URL can be trivially broken into a nice trail of breadcrumbs. Indeed, that's one test for good URL design -- the URL can be interpreted as breadcrumbs and displayed meaningfully to the users.
For a few view functions, where we present information that's part of a "many-to-many" join, for example, there are two candidate parents. The URL may say one thing, but the session's context stack says another.
For that reason, our view functions have to leave context clues in the session so we can emit breadcrumbs.
The Django admin view modules have automatic breadcumbs, which are implemented like this:
{% block breadcrumbs %}
<div class="breadcrumbs">
<a href="{% url 'admin:index' %}">{% trans 'Home' %}</a>
{% block crumbs %}
{% if title %} › {{ title }}{% endif %}
{% endblock %}
</div>
{% endblock %}
So there is some kind of built-in support for this..
Note: I provide the full snippet below, since djangosnippets has been finicky lately.
Cool, someone actually found my snippet :-) The use of my template tag is rather simple.
To answer your question there is no "built-in" django mechanism for dealing with breadcrumbs, but it does provide us with the next best thing: custom template tags.
Imagine you want to have breadcrumbs like so:
Services -> Programming
Services -> Consulting
Then you will probably have a few named urls: "services", and "programming", "consulting":
(r'^services/$',
'core.views.services',
{},
'services'),
(r'^services/programming$',
'core.views.programming',
{},
'programming'),
(r'^services/consulting$',
'core.views.consulting',
{},
'consulting'),
Now inside your html template (lets just look at consulting page) all you have to put is:
//consulting.html
{% load breadcrumbs %}
{% block breadcrumbs %}
{% breadcrumb_url 'Services' services %}
{% breadcrumb_url 'Consulting' consulting %}
{% endblock %}
If you want to use some kind of custom text within the breadcrumb, and don't want to link it, you can use breadcrumb tag instead.
//consulting.html
{% load breadcrumbs %}
{% block breadcrumbs %}
{% breadcrumb_url 'Services' services %}
{% breadcrumb_url 'Consulting' consulting %}
{% breadcrumb 'We are great!' %}
{% endblock %}
There are more involved situations where you might want to include an id of a particular object, which is also easy to do. This is an example that is more realistic:
{% load breadcrumbs %}
{% block breadcrumbs %}
{% breadcrumb_url 'Employees' employee_list %}
{% if employee.id %}
{% breadcrumb_url employee.company.name company_detail employee.company.id %}
{% breadcrumb_url employee.full_name employee_detail employee.id %}
{% breadcrumb 'Edit Employee ' %}
{% else %}
{% breadcrumb 'New Employee' %}
{% endif %}
{% endblock %}
DaGood breadcrumbs snippet
Provides two template tags to use in your HTML templates: breadcrumb and breadcrumb_url. The first allows creating of simple url, with the text portion and url portion. Or only unlinked text (as the last item in breadcrumb trail for example). The second, can actually take the named url with arguments! Additionally it takes a title as the first argument.
This is a templatetag file that should go into your /templatetags directory.
Just change the path of the image in the method create_crumb and you are good to go!
Don't forget to {% load breadcrumbs %} at the top of your html template!
from django import template
from django.template import loader, Node, Variable
from django.utils.encoding import smart_str, smart_unicode
from django.template.defaulttags import url
from django.template import VariableDoesNotExist
register = template.Library()
@register.tag
def breadcrumb(parser, token):
"""
Renders the breadcrumb.
Examples:
{% breadcrumb "Title of breadcrumb" url_var %}
{% breadcrumb context_var url_var %}
{% breadcrumb "Just the title" %}
{% breadcrumb just_context_var %}
Parameters:
-First parameter is the title of the crumb,
-Second (optional) parameter is the url variable to link to, produced by url tag, i.e.:
{% url person_detail object.id as person_url %}
then:
{% breadcrumb person.name person_url %}
@author Andriy Drozdyuk
"""
return BreadcrumbNode(token.split_contents()[1:])
@register.tag
def breadcrumb_url(parser, token):
"""
Same as breadcrumb
but instead of url context variable takes in all the
arguments URL tag takes.
{% breadcrumb "Title of breadcrumb" person_detail person.id %}
{% breadcrumb person.name person_detail person.id %}
"""
bits = token.split_contents()
if len(bits)==2:
return breadcrumb(parser, token)
# Extract our extra title parameter
title = bits.pop(1)
token.contents = ' '.join(bits)
url_node = url(parser, token)
return UrlBreadcrumbNode(title, url_node)
class BreadcrumbNode(Node):
def __init__(self, vars):
"""
First var is title, second var is url context variable
"""
self.vars = map(Variable,vars)
def render(self, context):
title = self.vars[0].var
if title.find("'")==-1 and title.find('"')==-1:
try:
val = self.vars[0]
title = val.resolve(context)
except:
title = ''
else:
title=title.strip("'").strip('"')
title=smart_unicode(title)
url = None
if len(self.vars)>1:
val = self.vars[1]
try:
url = val.resolve(context)
except VariableDoesNotExist:
print 'URL does not exist', val
url = None
return create_crumb(title, url)
class UrlBreadcrumbNode(Node):
def __init__(self, title, url_node):
self.title = Variable(title)
self.url_node = url_node
def render(self, context):
title = self.title.var
if title.find("'")==-1 and title.find('"')==-1:
try:
val = self.title
title = val.resolve(context)
except:
title = ''
else:
title=title.strip("'").strip('"')
title=smart_unicode(title)
url = self.url_node.render(context)
return create_crumb(title, url)
def create_crumb(title, url=None):
"""
Helper function
"""
crumb = """<span class="breadcrumbs-arrow">""" \
"""<img src="/media/images/arrow.gif" alt="Arrow">""" \
"""</span>"""
if url:
crumb = "%s<a href='%s'>%s</a>" % (crumb, url, title)
else:
crumb = "%s %s" % (crumb, title)
return crumb