Django - minimal form

Posted under » Django on 6 May 2021

Let’s update our poll detail template (“polls/detail.html”) from the last tutorial, so that the template contains an HTML <form> element:

<h1>{{ question.question_text }}</h1>

{% if error_message %}<p><strong>{{ error_message }}</strong></p>{% endif %}

<form action="{% url 'polls:vote' question.id %}" method="post">
{% csrf_token %}
{% for choice in question.choice_set.all %}
    <input type="radio" name="choice" id="choice{{ forloop.counter }}" value="{{ choice.id }}">
    <label for="choice{{ forloop.counter }}">{{ choice.choice_text }}</label><br>
{% endfor %}
<input type="submit" value="Vote">
</form>

Remember, we created a URLconf for the polls application that includes this line:

path('<int:question_id>/vote/', views.vote, name='vote'),

Now, let’s create a Django view that handles the submitted data. Add the following to polls/views.py:

from django.http import HttpResponse, HttpResponseRedirect
from django.shortcuts import get_object_or_404, render
from .models import Choice, Question
from django.urls import reverse

def vote(request, question_id):
    question = get_object_or_404(Question, pk=question_id)
    try:
        selected_choice = question.choice_set.get(pk=request.POST['choice'])
    except (KeyError, Choice.DoesNotExist):
        # Redisplay the question voting form.
        return render(request, 'polls/detail.html', {
            'question': question,
            'error_message': "You didn't select a choice.",
        })
    else:
        selected_choice.votes += 1
        selected_choice.save()
        # 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(reverse('polls:results', args=(question.id,)))
'/polls/3/results/'

In the template tutorial, request is an HttpRequest object

detail(request=, question_id=34)

The question_id=34 part comes from <int:question_id>. Using angle brackets “captures” part of the URL and sends it as a keyword argument to the view function. The :question_id> part of the string defines the name that will be used to identify the matched pattern, and the <int: part is a converter that determines what patterns should match this part of the URL path

After somebody votes in a question, the vote() view redirects to the results page for the question. Let’s write that view.py:

def results(request, question_id):
    question = get_object_or_404(Question, pk=question_id)
    return render(request, 'polls/results.html', {'question': question})

and let's do the polls/results.html.

<h1>{{ question.question_text }}</h1>

<ul>
{% for choice in question.choice_set.all %}
    <li>{{ choice.choice_text }} -- {{ choice.votes }} vote{{ choice.votes|pluralize }}</li>
{% endfor %}
</ul>

<a href="{% url 'polls:detail' question.id %}">Vote again?</a>

Now, go to /polls/1/ in your browser and vote in the question. 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.

let’s use Django’s own database API and use the API for our views.

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