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Diffstat (limited to 'docs/intro/tutorial03.txt')
| -rw-r--r-- | docs/intro/tutorial03.txt | 127 |
1 files changed, 66 insertions, 61 deletions
diff --git a/docs/intro/tutorial03.txt b/docs/intro/tutorial03.txt index 1165fbf18a..06707f2da8 100644 --- a/docs/intro/tutorial03.txt +++ b/docs/intro/tutorial03.txt @@ -29,15 +29,15 @@ application, you might have the following views: In our poll application, we'll have the following four views: -* Poll "index" page -- displays the latest few polls. +* Question "index" page -- displays the latest few questions. -* Poll "detail" page -- displays a poll question, with no results but +* Question "detail" page -- displays a question text, with no results but with a form to vote. -* Poll "results" page -- displays results for a particular poll. +* Question "results" page -- displays results for a particular question. * Vote action -- handles voting for a particular choice in a particular - poll. + question. In Django, web pages and other content are delivered by views. Each view is represented by a simple Python function (or method, in the case of class-based @@ -66,8 +66,9 @@ and put the following Python code in it:: from django.http import HttpResponse + def index(request): - return HttpResponse("Hello, world. You're at the poll index.") + return HttpResponse("Hello, world. You're at the polls index.") This is the simplest view possible in Django. To call the view, we need to map it to a URL - and for this we need a URLconf. @@ -109,7 +110,7 @@ with:: You have now wired an ``index`` view into the URLconf. Go to http://localhost:8000/polls/ in your browser, and you should see the text -"*Hello, world. You're at the poll index.*", which you defined in the +"*Hello, world. You're at the polls index.*", which you defined in the ``index`` view. The :func:`~django.conf.urls.url` function is passed four arguments, two @@ -173,14 +174,15 @@ Writing more views Now let's add a few more views to ``polls/views.py``. These views are slightly different, because they take an argument:: - def detail(request, poll_id): - return HttpResponse("You're looking at poll %s." % poll_id) + def detail(request, question_id): + return HttpResponse("You're looking at question %s." % question_id) - def results(request, poll_id): - return HttpResponse("You're looking at the results of poll %s." % poll_id) + def results(request, question_id): + response = "You're looking at the results of question %s." + return HttpResponse(response % question_id) - def vote(request, poll_id): - return HttpResponse("You're voting on poll %s." % poll_id) + def vote(request, question_id): + return HttpResponse("You're voting on question %s." % question_id) Wire these new views into the ``polls.urls`` module by adding the following :func:`~django.conf.urls.url` calls:: @@ -193,11 +195,11 @@ Wire these new views into the ``polls.urls`` module by adding the following # ex: /polls/ url(r'^$', views.index, name='index'), # ex: /polls/5/ - url(r'^(?P<poll_id>\d+)/$', views.detail, name='detail'), + url(r'^(?P<question_id>\d+)/$', views.detail, name='detail'), # ex: /polls/5/results/ - url(r'^(?P<poll_id>\d+)/results/$', views.results, name='results'), + url(r'^(?P<question_id>\d+)/results/$', views.results, name='results'), # ex: /polls/5/vote/ - url(r'^(?P<poll_id>\d+)/vote/$', views.vote, name='vote'), + url(r'^(?P<question_id>\d+)/vote/$', views.vote, name='vote'), ) Take a look in your browser, at "/polls/34/". It'll run the ``detail()`` @@ -229,14 +231,14 @@ Here's what happens if a user goes to "/polls/34/" in this system: * Then, Django will strip off the matching text (``"polls/"``) and send the remaining text -- ``"34/"`` -- to the 'polls.urls' URLconf for - further processing which matches ``r'^(?P<poll_id>\d+)/$'`` resulting in a + further processing which matches ``r'^(?P<question_id>\d+)/$'`` resulting in a call to the ``detail()`` view like so:: - detail(request=<HttpRequest object>, poll_id='34') + detail(request=<HttpRequest object>, question_id='34') -The ``poll_id='34'`` part comes from ``(?P<poll_id>\d+)``. Using parentheses +The ``question_id='34'`` part comes from ``(?P<question_id>\d+)``. Using parentheses around a pattern "captures" the text matched by that pattern and sends it as an -argument to the view function; ``?P<poll_id>`` defines the name that will +argument to the view function; ``?P<question_id>`` defines the name that will be used to identify the matched pattern; and ``\d+`` is a regular expression to match a sequence of digits (i.e., a number). @@ -271,11 +273,12 @@ commas, according to publication date:: from django.http import HttpResponse - from polls.models import Poll + from polls.models import Question + def index(request): - latest_poll_list = Poll.objects.order_by('-pub_date')[:5] - output = ', '.join([p.question for p in latest_poll_list]) + latest_question_list = Question.objects.order_by('-pub_date')[:5] + output = ', '.join([p.question_text for p in latest_question_list]) return HttpResponse(output) There's a problem here, though: the page's design is hard-coded in the view. If @@ -326,10 +329,10 @@ Put the following code in that template: .. code-block:: html+django - {% if latest_poll_list %} + {% if latest_question_list %} <ul> - {% for poll in latest_poll_list %} - <li><a href="/polls/{{ poll.id }}/">{{ poll.question }}</a></li> + {% for question in latest_question_list %} + <li><a href="/polls/{{ question.id }}/">{{ question.question_text }}</a></li> {% endfor %} </ul> {% else %} @@ -341,13 +344,14 @@ Now let's update our ``index`` view in ``polls/views.py`` to use the template:: from django.http import HttpResponse from django.template import RequestContext, loader - from polls.models import Poll + from polls.models import Question + def index(request): - latest_poll_list = Poll.objects.order_by('-pub_date')[:5] + latest_question_list = Question.objects.order_by('-pub_date')[:5] template = loader.get_template('polls/index.html') context = RequestContext(request, { - 'latest_poll_list': latest_poll_list, + 'latest_question_list': latest_question_list, }) return HttpResponse(template.render(context)) @@ -356,8 +360,8 @@ context. The context is a dictionary mapping template variable names to Python objects. Load the page by pointing your browser at "/polls/", and you should see a -bulleted-list containing the "What's up" poll from Tutorial 1. The link points -to the poll's detail page. +bulleted-list containing the "What's up" question from Tutorial 1. The link points +to the question's detail page. A shortcut: :func:`~django.shortcuts.render` -------------------------------------------- @@ -369,11 +373,12 @@ rewritten:: from django.shortcuts import render - from polls.models import Poll + from polls.models import Question + def index(request): - latest_poll_list = Poll.objects.all().order_by('-pub_date')[:5] - context = {'latest_poll_list': latest_poll_list} + latest_question_list = Question.objects.all().order_by('-pub_date')[:5] + context = {'latest_question_list': latest_question_list} return render(request, 'polls/index.html', context) Note that once we've done this in all these views, we no longer need to import @@ -389,29 +394,29 @@ object of the given template rendered with the given context. Raising a 404 error =================== -Now, let's tackle the poll detail view -- the page that displays the question +Now, let's tackle the question detail view -- the page that displays the question text for a given poll. Here's the view:: from django.http import Http404 from django.shortcuts import render - from polls.models import Poll + from polls.models import Question # ... - def detail(request, poll_id): + def detail(request, question_id): try: - poll = Poll.objects.get(pk=poll_id) - except Poll.DoesNotExist: + question = Question.objects.get(pk=question_id) + except Question.DoesNotExist: raise Http404 - return render(request, 'polls/detail.html', {'poll': poll}) + return render(request, 'polls/detail.html', {'question': question}) The new concept here: The view raises the :exc:`~django.http.Http404` exception -if a poll with the requested ID doesn't exist. +if a question with the requested ID doesn't exist. We'll discuss what you could put in that ``polls/detail.html`` template a bit later, but if you'd like to quickly get the above example working, a file containing just:: - {{ poll }} + {{ question }} will get you started for now. @@ -424,11 +429,11 @@ provides a shortcut. Here's the ``detail()`` view, rewritten:: from django.shortcuts import render, get_object_or_404 - from polls.models import Poll + from polls.models import Question # ... - def detail(request, poll_id): - poll = get_object_or_404(Poll, pk=poll_id) - return render(request, 'polls/detail.html', {'poll': poll}) + def detail(request, question_id): + question = get_object_or_404(Question, pk=question_id) + return render(request, 'polls/detail.html', {'question': question}) The :func:`~django.shortcuts.get_object_or_404` function takes a Django model as its first argument and an arbitrary number of keyword arguments, which it @@ -458,27 +463,27 @@ Use the template system ======================= Back to the ``detail()`` view for our poll application. Given the context -variable ``poll``, here's what the ``polls/detail.html`` template might look +variable ``question``, here's what the ``polls/detail.html`` template might look like: .. code-block:: html+django - <h1>{{ poll.question }}</h1> + <h1>{{ question.question_text }}</h1> <ul> - {% for choice in poll.choice_set.all %} + {% for choice in question.choice_set.all %} <li>{{ choice.choice_text }}</li> {% endfor %} </ul> The template system uses dot-lookup syntax to access variable attributes. In -the example of ``{{ poll.question }}``, first Django does a dictionary lookup -on the object ``poll``. Failing that, it tries an attribute lookup -- which +the example of ``{{ question.question_text }}``, first Django does a dictionary lookup +on the object ``question``. Failing that, it tries an attribute lookup -- which works, in this case. If attribute lookup had failed, it would've tried a list-index lookup. Method-calling happens in the :ttag:`{% for %}<for>` loop: -``poll.choice_set.all`` is interpreted as the Python code -``poll.choice_set.all()``, which returns an iterable of ``Choice`` objects and is +``question.choice_set.all`` is interpreted as the Python code +``question.choice_set.all()``, which returns an iterable of ``Choice`` objects and is suitable for use in the :ttag:`{% for %}<for>` tag. See the :doc:`template guide </topics/templates>` for more about templates. @@ -486,12 +491,12 @@ See the :doc:`template guide </topics/templates>` for more about templates. Removing hardcoded URLs in templates ==================================== -Remember, when we wrote the link to a poll in the ``polls/index.html`` +Remember, when we wrote the link to a question in the ``polls/index.html`` template, the link was partially hardcoded like this: .. code-block:: html+django - <li><a href="/polls/{{ poll.id }}/">{{ poll.question }}</a></li> + <li><a href="/polls/{{ question.id }}/">{{ question.question_text }}</a></li> The problem with this hardcoded, tightly-coupled approach is that it becomes challenging to change URLs on projects with a lot of templates. However, since @@ -501,12 +506,12 @@ defined in your url configurations by using the ``{% url %}`` template tag: .. code-block:: html+django - <li><a href="{% url 'detail' poll.id %}">{{ poll.question }}</a></li> + <li><a href="{% url 'detail' question.id %}">{{ question.question_text }}</a></li> .. note:: - If ``{% url 'detail' poll.id %}`` (with quotes) doesn't work, but - ``{% url detail poll.id %}`` (without quotes) does, that means you're + If ``{% url 'detail' question.id %}`` (with quotes) doesn't work, but + ``{% url detail question.id %}`` (without quotes) does, that means you're using a version of Django < 1.5. In this case, add the following declaration at the top of your template: @@ -520,7 +525,7 @@ defined below:: ... # the 'name' value as called by the {% url %} template tag - url(r'^(?P<poll_id>\d+)/$', views.detail, name='detail'), + url(r'^(?P<question_id>\d+)/$', views.detail, name='detail'), ... If you want to change the URL of the polls detail view to something else, @@ -529,7 +534,7 @@ template (or templates) you would change it in ``polls/urls.py``:: ... # added the word 'specifics' - url(r'^specifics/(?P<poll_id>\d+)/$', views.detail, name='detail'), + url(r'^specifics/(?P<question_id>\d+)/$', views.detail, name='detail'), ... Namespacing URL names @@ -560,13 +565,13 @@ Now change your ``polls/index.html`` template from: .. code-block:: html+django - <li><a href="{% url 'detail' poll.id %}">{{ poll.question }}</a></li> + <li><a href="{% url 'detail' question.id %}">{{ question.question_text }}</a></li> to point at the namespaced detail view: .. code-block:: html+django - <li><a href="{% url 'polls:detail' poll.id %}">{{ poll.question }}</a></li> + <li><a href="{% url 'polls:detail' question.id %}">{{ question.question_text }}</a></li> When you're comfortable with writing views, read :doc:`part 4 of this tutorial </intro/tutorial04>` to learn about simple form processing and generic views. |