The Zen of Admin

At its core, Djangos admin interface is designed for a single activity:

Trusted users editing structured content.

Yes, its extremely simple but that simplicity is based on a whole host of assumptions. The entire philosophy of Djangos admin interface follows directly from these assumptions, so lets dig into the subtext of this phrase in the sections that follow.

Customizing Admin Templates

Out of the box, Django provides a number of tools for customizing the built-in admin templates, which well go over shortly, but for tasks beyond that (e.g., anything requiring custom workflow or granular permissions), youll need to read the section titled Creating Custom Admin Views later in this chapter.

For now, though, lets look at some quick ways of customizing the appearance (and, to some extent, behavior) of the admin interface. Chapter 6 covers a few of the most common tasks: rebranding the Django admin interface (for those pointy-haired bosses who hate blue) and providing a custom admin form.

Past that point, the goal usually involves changing some of the templates for a particular item. Each of the admin views the change lists, edit forms, delete confirmation pages, and history views has an associated template that can be overridden in a number of ways.

First, you can override the template globally. The admin view looks for templates using the standard template-loading mechanism, so if you create templates in one of your template directories, Django will load those instead of the default admin templates bundled with Django. These global templates are outlined in Table 17-1.

Most of the time, however, youll want to change the template for just a single object or application (not globally). Thus, each admin view looks for model- and application-specific templates first. Those views look for templates in this order:

• admin/<app_label>/<object_name>/<template>.html

• admin/<app_label>/<template>.html

• admin/<template>.html

For example, the add/edit form view for a Book model in the books application looks for templates in this order:

• admin/books/book/change_form.html

• admin/books/change_form.html

• admin/change_form.html

Custom Model Templates

Most of the time, youll want to use the first template to create a model-specific template. This is usually best done by extending the base template and adding information to one of the blocks defined in that template.

For example, say we want to add a little bit of help text to the top of that book page. Maybe something like the form shown in Figure 17-1.

Figure 17-1. A customized admin edit form

This is pretty easy to do: simply create a template called admin/bookstore/book/change_form.html and insert this code:

{% extends "admin/change_form.html" %}

{% block form_top %}
  <p>Insert meaningful help message here...</p>
{% endblock %}

All these templates define a number of blocks you can override. As with most programs, the best documentation is the code, so we encourage you to look through the admin templates (theyre in django/contrib/admin/templates/ ) for the most up-to-date information.

{% extends "admin/object_history.html" %}

{% block extrahead %}
    <script src="http://media.example.com/javascript/jquery.js" type="text/javascript"></script>
    <script type="text/javascript">

        // code to actually use jQuery here...

    </script>
{% endblock %}

Creating Custom Admin Views

At this point, anyone looking to add custom behavior to Djangos admin interface is probably starting to get a bit frustrated. All youve talked about is how to change the admin interface visually , we hear them cry. But how do I change the way the admin interface works ?

The first thing to understand is that its not magic . That is, nothing the admin interface does is special in any way the admin interface is just a set of views (they live in django.contrib.admin.views ) that manipulate data just like any other view.

Sure, theres quite a bit of code in there; it has to deal with all the various options, field types, and settings that influence model behavior. Still, when you realize that the admin interface is just a set of views, adding custom admin views becomes easier to understand.

By way of example, lets add a publisher report view to our book application from Chapter 6. Well build an admin view that shows the list of books broken down by publisher a pretty typical example of a custom admin report view you might need to build.

First, lets wire up a view in our URLconf. We need to insert this line:

(r'^admin/books/report/$', 'mysite.books.admin_views.report'),

before the line including the admin views. A bare-bones URLconf might look like this:

from django.conf.urls.defaults import *

urlpatterns = patterns('',
    (r'^admin/bookstore/report/$', 'bookstore.admin_views.report'),
    (r'^admin/', include('django.contrib.admin.urls')),
)

Why put the custom view before the admin inclusion? Recall that Django processes URL patterns in order. The admin inclusion matches nearly anything that falls under the inclusion point, so if we reverse the order of those lines, Django will find a built-in admin view for that pattern, which wont work. In this particular case, it will try to load a change list for a Report model in the books application, which doesnt exist.

Now lets write our view. For the sake of simplicity, well just load all books into the context and let the template handle the grouping with the {% regroup %} tag. Create a file, books/admin_views.py , with this code:

from mysite.books.models import Book
from django.template import RequestContext
from django.shortcuts import render_to_response
from django.contrib.admin.views.decorators import staff_member_required


def report(request):
    return render_to_response(
        "admin/books/report.html",
        {'book_list' : Book.objects.all()},
        RequestContext(request, {}),
    )
report = staff_member_required(report)

Because we left the grouping up to the template, this view is pretty simple. However, there are some subtle bits here worth making explicit:

We use the staff_member_required decorator from django.contrib.admin.views.decorators . This is similar to the login_required decorator discussed in Chapter 12, but this decorator also checks that the given user is marked as a staff member, and thus is allowed access to the admin interface.

This decorator protects all the built-in admin views and makes the authentication logic for your view match the rest of the admin interface.

We render a template located under admin/ . While this isnt strictly required, its considered good practice to keep all your admin templates grouped in an admin directory. Weve also put the template in a directory named books after our application also a best practice.

We use RequestContext as the third parameter (context_instance ) to render_to_response . This ensures that information about the current user is available to the template.

See Chapter 10 for more about RequestContext .

Finally, well make a template for this view. Well extend the built-in admin templates to make this view visually appear to be part of the admin interface:

{% extends "admin/base_site.html" %}

{% block title %}List of books by publisher{% endblock %}

{% block content %}
<div id="content-main">
  <h1>List of books by publisher:</h1>
  {% regroup book_list|dictsort:"publisher.name" by publisher as books_by_publisher %}
  {% for publisher in books_by_publisher %}
    <h3>{{ publisher.grouper }}</h3>
    <ul>
      {% for book in publisher.list|dictsort:"title" %}
        <li>{{ book }}</li>
      {% endfor %}
    </ul>
  {% endfor %}
</div>
{% endblock %}

By extending admin/base_site.html , we get the look and feel of the Django admin for free. Figure 17-2 shows what the end result looks like.

Figure 17-2. A custom books by publisher admin view

You can use this technique to add anything you can dream of to the admin interface. Remember that these so-called custom admin views are really just normal Django views; you can use all the techniques you learn in the rest of this book to provide as complex an admin interface as you need.

Well close out this chapter with some ideas for custom admin views.

Overriding Built-in Views

At times the default admin views just dont cut it. You can easily swap in your own custom view for any stage of the admin interface; just let your URL shadow the built-in admin one. That is, if your view comes before the default admin view in the URLconf, your view will be called instead of the default one.

For example, we could replace the built-in create view for a book with a form that lets the user simply enter an ISBN. We could then look up the books information from http://isbn.nu/ and create the object automatically.

The code for such a view is left as an exercise for the reader, but the important part is this URLconf snippet:

(r'^admin/bookstore/book/add/$', 'mysite.books.admin_views.add_by_isbn'),

If this bit comes before the admin URLs in your URLconf, the add_by_isbn view will completely replace the standard admin view.

We could follow a similar tack to replace a delete confirmation page, the edit page, or any other part of the admin interface.

Whats Next?

If youre a native English speakerand we expect that many readers of this English-language book areyou might not have noticed one of the coolest features of the admin interface: its available in almost 40 different languages! This is made possible by Djangos internationalization framework (and the hard work of Djangos volunteer translators). The next chapter explains how to use this framework to provide localized Django sites.

Avanti!