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Diffstat (limited to 'docs/tutorial04.txt')
| -rw-r--r-- | docs/tutorial04.txt | 49 |
1 files changed, 43 insertions, 6 deletions
diff --git a/docs/tutorial04.txt b/docs/tutorial04.txt index 49ed649cff..5cc12c445d 100644 --- a/docs/tutorial04.txt +++ b/docs/tutorial04.txt @@ -48,6 +48,7 @@ So let's create a ``vote()`` function in ``mysite/polls/views.py``:: from django.shortcuts import get_object_or_404, render_to_response from django.http import HttpResponseRedirect + from django.core.urlresolvers import reverse from mysite.polls.models import Choice, Poll # ... def vote(request, poll_id): @@ -66,7 +67,7 @@ So let's create a ``vote()`` function in ``mysite/polls/views.py``:: # Always return an HttpResponseRedirect after successfully dealing # with POST data. This prevents data from being posted twice if a # user hits the Back button. - return HttpResponseRedirect('/polls/%s/results/' % p.id) + return HttpResponseRedirect(reverse('mysite.polls.views.results', args=(p.id,))) This code includes a few things we haven't covered yet in this tutorial: @@ -86,13 +87,29 @@ This code includes a few things we haven't covered yet in this tutorial: * After incrementing the choice count, the code returns an ``HttpResponseRedirect`` rather than a normal ``HttpResponse``. ``HttpResponseRedirect`` takes a single argument: the URL to which the - user will be redirected. You should leave off the "http://" and domain - name if you can. That helps your app become portable across domains. + user will be redirected (see the following point for how we construct + the URL in this case). As the Python comment above points out, you should always return an ``HttpResponseRedirect`` after successfully dealing with POST data. This tip isn't specific to Django; it's just good Web development practice. + * We are using the ``reverse()`` function in the ``HttpResponseRedirect`` + constructor in this example. This function helps avoid having to + hardcode a URL in the view function. It is given the name of the view + that we want to pass control to and the variable portion of the URL + pattern that points to that view. In this case, using the URLConf we set + up in Tutorial 3, this ``reverse()`` call will return a string like :: + + '/polls/3/results/' + + ... where the ``3`` is the value of ``p.id``. This redirected URL will + then call the ``'results'`` view to display the final page. Note that + you need to use the full name of the view here (including the prefix). + + For more information about ``reverse()``, see the `URL dispatcher`_ + documentation. + As mentioned in Tutorial 3, ``request`` is a ``HTTPRequest`` object. For more on ``HTTPRequest`` objects, see the `request and response documentation`_. @@ -120,7 +137,8 @@ Now, go to ``/polls/1/`` in your browser and vote in the poll. You should see a results page that gets updated each time you vote. If you submit the form without having chosen a choice, you should see the error message. -.. _request and response documentation: http://www.djangoproject.com/documentation/request_response/ +.. _request and response documentation: ../request_response/ +.. _URL dispatcher: ../url_dispatch#reverse Use generic views: Less code is better ====================================== @@ -206,6 +224,21 @@ for the polls app, we manually specify a template name for the results view: ``template_name='polls/results.html'``. Otherwise, both views would use the same template. Note that we use ``dict()`` to return an altered dictionary in place. +.. note:: ``all()`` is lazy + + It might look a little frightening to see ``Poll.objects.all()`` being used + in a detail view which only needs one ``Poll`` object, but don't worry; + ``Poll.objects.all()`` is actually a special object called a ``QuerySet``, + which is "lazy" and doesn't hit your database until it absolutely has to. By + the time the database query happens, the ``object_detail`` generic view will + have narrowed its scope down to a single object, so the eventual query will + only select one row from the database. + + If you'd like to know more about how that works, The Django database API + documentation `explains the lazy nature of QuerySet objects`_. + +.. _explains the lazy nature of QuerySet objects: ../db-api/#querysets-are-lazy + In previous parts of the tutorial, the templates have been provided with a context that contains the ``poll`` and ``latest_poll_list`` context variables. However, the generic views provide the variables ``object`` and ``object_list`` as context. @@ -226,7 +259,7 @@ Run the server, and use your new polling app based on generic views. For full details on generic views, see the `generic views documentation`_. -.. _generic views documentation: http://www.djangoproject.com/documentation/generic_views/ +.. _generic views documentation: ../generic_views/ Coming soon =========== @@ -241,4 +274,8 @@ installments: * Advanced admin features: Permissions * Advanced admin features: Custom JavaScript -.. _Tutorial 3: http://www.djangoproject.com/documentation/tutorial3/ +In the meantime, you can read through the rest of the `Django documentation`_ +and start writing your own applications. + +.. _Tutorial 3: ../tutorial03/ +.. _Django documentation: http://www.djangoproject.com/documentation/ |