Learning Django by Example(11) Attach a tag


Tag is probably the most distinguish feature of Web 2.0 applications that differentiate them from the traditional hierarchy categories. I want to attach a Web 2.0 tag to Gelman, so the user could simply click the tag, and find the related books that may arouse his/her interest.

django-tagging is a generic tag application to simplify the backend development, all you need to do is just add the _TagField_to the _Book_model:

class Book(models.Model):
    tags = TagField()

And in the book_detail.html template, refer it as object.tags as this:

{{ object.tags|popuptags|safe }}

popuptags is a custom tag that decorates the tags as a list of HTML links, and join them:

def popuptags(value):
    tags = value.split(" ")
    return " ".join(['[%s](/bookshelf/tags/%s)' % (x, x) for x in tags])

So tag foo is linked with /bookshelf/tags/foo, so just redirect the request to the view:

(r'^tags/(?P[\w-]+)/$', views.by_tag)

And handle it in views.py:

def by_tag(request, tag_name):
    tag = Tag.objects.get(name=tag_name)
    return list_detail.object_list(
        queryset=TaggedItem.objects.get_by_model(Book, tag),
        extra_context={'title': 'Tagged by %s' % tag_name},

All the tedious work has been handled by django-tagging: we first get a tag object by name, and then build a QuerySet using get_by_model method; the rest is handled by the generic view, done. Salute to django-tagging developers!

We would discuss how to add a tag in the next post, that is the magic of Dojo.