Changed overview and tutorial docs to use render_to_response and get_object_or_404, to cut down on code
git-svn-id: http://code.djangoproject.com/svn/django/trunk@678 bcc190cf-cafb-0310-a4f2-bffc1f526a37
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Adrian Holovaty
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@ -195,20 +195,10 @@ Generally, a view retrieves data according to the parameters, loads a template
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and renders the template with the retrieved data. Here's an example view for
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article_detail from above::
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from django.models.news import articles
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def article_detail(request, year, month, article_id):
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# Use the Django API to find an object matching the URL criteria.
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try:
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a = articles.get_object(pub_date__year=year, pub_date__month=month, pk=article_id)
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except articles.ArticleDoesNotExist:
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raise Http404
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t = template_loader.get_template('news/article_detail')
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c = Context(request, {
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'article': a,
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})
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content = t.render(c)
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return HttpResponse(content)
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a = get_object_or_404(articles, pub_date__year=year, pub_date__month=month, pk=article_id)
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return render_to_response('news/article_detail', {'article': a})
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This example uses Django's template system, which has several key features.
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@ -261,7 +251,6 @@ template has to define only what's unique to that template.
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Here's what the "base" template might look like::
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<html>
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<head>
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<title>{% block title %}{% endblock %}</title>
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@ -192,14 +192,14 @@ you want to change the way the page looks, you'll have to edit this Python code.
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So let's use Django's template system to separate the design from Python::
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from django.core import template_loader
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from django.core.extensions import DjangoContext as Context
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from django.core.template import Context
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from django.models.polls import polls
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from django.utils.httpwrappers import HttpResponse
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def index(request):
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latest_poll_list = polls.get_list(order_by=['-pub_date'], limit=5)
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t = template_loader.get_template('polls/index')
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c = Context(request, {
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c = Context({
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'latest_poll_list': latest_poll_list,
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})
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return HttpResponse(t.render(c))
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@ -242,6 +242,27 @@ Put the following code in that template::
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Load the page in your Web browser, and you should see a bulleted-list
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containing the "What's up" poll from Tutorial 1.
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A shortcut: render_to_response()
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--------------------------------
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It's a very common idiom to load a template, fill a context and return an
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``HttpResponse`` object with the result of the rendered template. Django
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provides a shortcut. Here's the full ``index()`` view, rewritten::
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from django.core.extensions import render_to_response
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from django.models.polls import polls
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def index(request):
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latest_poll_list = polls.get_list(order_by=['-pub_date'], limit=5)
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return render_to_response('polls/index', {'latest_poll_list': latest_poll_list})
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Note that we no longer need to import ``template_loader``, ``Context`` or
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``HttpResponse``.
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The ``render_to_response()`` function takes a template name as its first
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argument and a dictionary as its optional second argument. It returns an
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``HttpResponse`` object of the given template rendered with the given context.
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Raising 404
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===========
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@ -254,15 +275,41 @@ for a given poll. Here's the view::
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p = polls.get_object(pk=poll_id)
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except polls.PollDoesNotExist:
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raise Http404
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t = template_loader.get_template('polls/detail')
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c = Context(request, {
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'poll': p,
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})
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return HttpResponse(t.render(c))
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return render_to_response('polls/detail', {'poll': p})
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The new concept here: The view raises the ``django.core.exceptions.Http404``
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exception if a poll with the requested ID doesn't exist.
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A shortcut: get_object_or_404()
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-------------------------------
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It's a very common idiom to use ``get_object()`` and raise ``Http404`` if the
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object doesn't exist. Django provides a shortcut. Here's the ``detail()`` view,
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rewritten:
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from django.core.extensions import get_object_or_404
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def detail(request, poll_id):
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p = get_object_or_404(polls, pk=poll_id)
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return render_to_response('polls/detail', {'poll': p})
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The ``get_object_or_404()`` function takes a Django model module as its first
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argument and an arbitrary number of keyword arguments, which it passes to the
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module's ``get_object()`` function. It raises ``Http404`` if the object doesn't
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exist.
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.. admonition:: Philosophy
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Why do we use a helper function ``get_object_or_404()`` instead of
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automatically catching the ``*DoesNotExist`` exceptions at a higher level,
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or having the model API raise ``Http404`` instead of ``*DoesNotExist``?
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Because that would couple the model layer to the view layer. One of the
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foremost design goals of Django is to maintain loose coupling.
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There's also a ``get_list_or_404()`` function, which works just as
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``get_object_or_404()`` -- except using ``get_list()`` instead of
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``get_object()``. It raises ``Http404`` if the list is empty.
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Write a 404 (page not found) view
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=================================
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@ -48,27 +48,20 @@ included this line::
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So let's create a ``vote()`` function in ``myproject/apps/polls/views/polls.py``::
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from django.core import template_loader
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from django.core.extensions import DjangoContext as Context
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from django.core.extensions import get_object_or_404, render_to_response
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from django.models.polls import choices, polls
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from django.utils.httpwrappers import HttpResponse, HttpResponseRedirect
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from django.core.exceptions import Http404
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from django.utils.httpwrappers import HttpResponseRedirect
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def vote(request, poll_id):
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try:
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p = polls.get_object(pk=poll_id)
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except polls.PollDoesNotExist:
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raise Http404
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p = get_object_or_404(polls, pk=poll_id)
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try:
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selected_choice = p.get_choice(pk=request.POST['choice'])
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except (KeyError, choices.ChoiceDoesNotExist):
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# Redisplay the poll voting form.
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t = template_loader.get_template('polls/detail')
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c = Context(request, {
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return render_to_response('polls/detail', {
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'poll': p,
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'error_message': "You didn't select a choice.",
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})
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return HttpResponse(t.render(c))
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else:
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selected_choice.votes += 1
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selected_choice.save()
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@ -109,15 +102,8 @@ 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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try:
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p = polls.get_object(pk=poll_id)
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except polls.PollDoesNotExist:
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raise Http404
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t = template_loader.get_template('polls/results')
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c = Context(request, {
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'poll': p,
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})
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return HttpResponse(t.render(c))
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p = get_object_or_404(polls, pk=poll_id)
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return render_to_response('polls/results', {'poll': p})
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This is almost exactly the same as the ``detail()`` view from `Tutorial 3`_.
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The only difference is the template name. We'll fix this redundancy later.
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