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Fixed #18715 - Refactored tutorial 3. Thank-you Daniel Greenfeld!
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Tim Graham
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3 changed files with 326 additions and 388 deletions
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@ -18,7 +18,7 @@ tutorial, so that the template contains an HTML ``<form>`` element:
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{% if error_message %}<p><strong>{{ error_message }}</strong></p>{% endif %}
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<form action="{% url 'polls.views.vote' poll.id %}" method="post">
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<form action="{% url 'polls:vote' poll.id %}" method="post">
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{% csrf_token %}
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{% for choice in poll.choice_set.all %}
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<input type="radio" name="choice" id="choice{{ forloop.counter }}" value="{{ choice.id }}" />
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@ -35,7 +35,7 @@ A quick rundown:
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selects one of the radio buttons and submits the form, it'll send the
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POST data ``choice=3``. This is HTML Forms 101.
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* We set the form's ``action`` to ``{% url 'polls.views.vote' poll.id %}``, and we
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* We set the form's ``action`` to ``{% url 'polls:vote' poll.id %}``, and we
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set ``method="post"``. Using ``method="post"`` (as opposed to
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``method="get"``) is very important, because the act of submitting this
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form will alter data server-side. Whenever you create a form that alters
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@ -52,34 +52,18 @@ A quick rundown:
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forms that are targeted at internal URLs should use the
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:ttag:`{% csrf_token %}<csrf_token>` template tag.
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The :ttag:`{% csrf_token %}<csrf_token>` tag requires information from the
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request object, which is not normally accessible from within the template
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context. To fix this, a small adjustment needs to be made to the ``detail``
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view, so that it looks like the following::
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from django.template import RequestContext
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# ...
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def detail(request, poll_id):
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p = get_object_or_404(Poll, pk=poll_id)
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return render_to_response('polls/detail.html', {'poll': p},
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context_instance=RequestContext(request))
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The details of how this works are explained in the documentation for
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:ref:`RequestContext <subclassing-context-requestcontext>`.
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Now, let's create a Django view that handles the submitted data and does
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something with it. Remember, in :doc:`Tutorial 3 </intro/tutorial03>`, we
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created a URLconf for the polls application that includes this line::
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(r'^(?P<poll_id>\d+)/vote/$', 'vote'),
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url(r'^(?P<poll_id>\d+)/vote/$', views.vote, name='vote'),
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We also created a dummy implementation of the ``vote()`` function. Let's
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create a real version. Add the following to ``polls/views.py``::
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from django.shortcuts import get_object_or_404, render_to_response
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from django.shortcuts import get_object_or_404, render
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from django.http import HttpResponseRedirect, HttpResponse
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from django.core.urlresolvers import reverse
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from django.template import RequestContext
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from polls.models import Choice, Poll
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# ...
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def vote(request, poll_id):
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@ -88,17 +72,17 @@ create a real version. Add the following to ``polls/views.py``::
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selected_choice = p.choice_set.get(pk=request.POST['choice'])
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except (KeyError, Choice.DoesNotExist):
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# Redisplay the poll voting form.
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return render_to_response('polls/detail.html', {
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return render(request, 'polls/detail.html', {
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'poll': p,
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'error_message': "You didn't select a choice.",
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}, context_instance=RequestContext(request))
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})
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else:
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selected_choice.votes += 1
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selected_choice.save()
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# Always return an HttpResponseRedirect after successfully dealing
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# with POST data. This prevents data from being posted twice if a
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# user hits the Back button.
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return HttpResponseRedirect(reverse('polls.views.results', args=(p.id,)))
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return HttpResponseRedirect(reverse('polls:results', args=(p.id,)))
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This code includes a few things we haven't covered yet in this tutorial:
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@ -142,8 +126,7 @@ This code includes a few things we haven't covered yet in this tutorial:
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'/polls/3/results/'
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... where the ``3`` is the value of ``p.id``. This redirected URL will
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then call the ``'results'`` view to display the final page. Note that you
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need to use the full name of the view here (including the prefix).
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then call the ``'results'`` view to display the final page.
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As mentioned in Tutorial 3, ``request`` is a :class:`~django.http.HttpRequest`
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object. For more on :class:`~django.http.HttpRequest` objects, see the
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@ -153,14 +136,14 @@ After somebody votes in a poll, the ``vote()`` view redirects to the results
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page for the poll. Let's write that view::
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def results(request, poll_id):
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p = get_object_or_404(Poll, pk=poll_id)
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return render_to_response('polls/results.html', {'poll': p})
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poll = get_object_or_404(Poll, pk=poll_id)
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return render(request, 'polls/results.html', {'poll': poll})
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This is almost exactly the same as the ``detail()`` view from :doc:`Tutorial 3
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</intro/tutorial03>`. The only difference is the template name. We'll fix this
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redundancy later.
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Now, create a ``results.html`` template:
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Now, create a ``polls/results.html`` template:
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.. code-block:: html+django
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@ -172,7 +155,7 @@ Now, create a ``results.html`` template:
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{% endfor %}
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</ul>
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<a href="{% url 'polls.views.detail' poll.id %}">Vote again?</a>
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<a href="{% url 'polls:detail' poll.id %}">Vote again?</a>
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Now, go to ``/polls/1/`` in your browser and vote in the poll. You should see a
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results page that gets updated each time you vote. If you submit the form
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@ -215,19 +198,7 @@ Read on for details.
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You should know basic math before you start using a calculator.
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First, open the ``polls/urls.py`` URLconf. It looks like this, according to the
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tutorial so far::
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from django.conf.urls import patterns, url
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urlpatterns = patterns('polls.views',
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url(r'^$', 'index'),
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url(r'^(?P<poll_id>\d+)/$', 'detail'),
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url(r'^(?P<poll_id>\d+)/results/$', 'results'),
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url(r'^(?P<poll_id>\d+)/vote/$', 'vote'),
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)
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Change it like so::
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First, open the ``polls/urls.py`` URLconf and change it like so::
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from django.conf.urls import patterns, url
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from django.views.generic import DetailView, ListView
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@ -239,18 +210,18 @@ Change it like so::
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queryset=Poll.objects.order_by('-pub_date')[:5],
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context_object_name='latest_poll_list',
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template_name='polls/index.html'),
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name='poll_index'),
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name='index'),
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url(r'^(?P<pk>\d+)/$',
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DetailView.as_view(
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model=Poll,
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template_name='polls/detail.html'),
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name='poll_detail'),
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name='detail'),
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url(r'^(?P<pk>\d+)/results/$',
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DetailView.as_view(
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model=Poll,
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template_name='polls/results.html'),
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name='poll_results'),
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url(r'^(?P<poll_id>\d+)/vote/$', 'polls.views.vote'),
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name='results'),
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url(r'^(?P<poll_id>\d+)/vote/$', 'polls.views.vote', name='vote'),
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)
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We're using two generic views here:
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@ -267,15 +238,6 @@ two views abstract the concepts of "display a list of objects" and
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``"pk"``, so we've changed ``poll_id`` to ``pk`` for the generic
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views.
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* We've added the ``name`` argument to the views (e.g. ``name='poll_results'``)
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so that we have a way to refer to their URL later on (see the
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documentation about :ref:`naming URL patterns
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<naming-url-patterns>` for information). We're also using the
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:func:`~django.conf.urls.url` function from
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:mod:`django.conf.urls` here. It's a good habit to use
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:func:`~django.conf.urls.url` when you are providing a
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pattern name like this.
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By default, the :class:`~django.views.generic.list.DetailView` generic
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view uses a template called ``<app name>/<model name>_detail.html``.
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In our case, it'll use the template ``"polls/poll_detail.html"``. The
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@ -308,41 +270,13 @@ You can now delete the ``index()``, ``detail()`` and ``results()``
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views from ``polls/views.py``. We don't need them anymore -- they have
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been replaced by generic views.
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The last thing to do is fix the URL handling to account for the use of
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generic views. In the vote view above, we used the
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:func:`~django.core.urlresolvers.reverse` function to avoid
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hard-coding our URLs. Now that we've switched to a generic view, we'll
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need to change the :func:`~django.core.urlresolvers.reverse` call to
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point back to our new generic view. We can't simply use the view
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function anymore -- generic views can be (and are) used multiple times
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-- but we can use the name we've given::
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return HttpResponseRedirect(reverse('poll_results', args=(p.id,)))
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The same rule apply for the :ttag:`url` template tag. For example in the
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``results.html`` template:
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.. code-block:: html+django
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<a href="{% url 'poll_detail' poll.id %}">Vote again?</a>
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Run the server, and use your new polling app based on generic views.
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For full details on generic views, see the :doc:`generic views documentation
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</topics/class-based-views/index>`.
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Coming soon
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===========
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What's next?
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============
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The tutorial ends here for the time being. Future installments of the tutorial
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will cover:
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* Advanced form processing
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* Using the RSS framework
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* Using the cache framework
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* Using the comments framework
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* Advanced admin features: Permissions
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* Advanced admin features: Custom JavaScript
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In the meantime, you might want to check out some pointers on :doc:`where to go
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from here </intro/whatsnext>`
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The tutorial ends here for the time being. In the meantime, you might want to
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check out some pointers on :doc:`where to go from here </intro/whatsnext>`.
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