Django tutorial summary for beginners by beginners ③ (View)

Introduction

This article is a series of steps through Django's official tutorials. This time, we will proceed with the third article, "Creating your first Django app, part 3."

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Creating your first Django app, part 3

https://docs.djangoproject.com/ja/3.0/intro/tutorial03/

Write more views

Add to polls / views.py.

polls/views.py

def detail(request, question_id):
    return HttpResponse("You're looking at question %s." % question_id)

def results(request, question_id):
    response = "You're looking at the results of question %s."
    return HttpResponse(response % question_id)

def vote(request, question_id):
    return HttpResponse("You're voting on question %s." % question_id)

Add it to polls / urls.py as well.

polls/urls.py

from django.urls import path

from . import views

urlpatterns = [
    # ex: /polls/
    path('', views.index, name='index'),
    # ex: /polls/5/
    path('<int:question_id>/', views.detail, name='detail'),
    # ex: /polls/5/results/
    path('<int:question_id>/results/', views.results, name='results'),
    # ex: /polls/5/vote/
    path('<int:question_id>/vote/', views.vote, name='vote'),
]

This sequence of steps is similar to routing work such as Rails.

Write a view that actually works

polls/views.py

from django.http import HttpResponse

from .models import Question


def index(request):
    latest_question_list = Question.objects.order_by('-pub_date')[:5]
    output = ', '.join([q.question_text for q in latest_question_list])
    return HttpResponse(output)

# Leave the rest of the views (detail, results, vote) unchanged

This is working, but I'll change it to use the Html template like Rails.

Inside the polls directory, create a templates / polls directory.

Create templeteʻindex.html for index.

polls/templates/polls/index.html

{% if latest_question_list %}
    <ul>
    {% for question in latest_question_list %}
        <li><a href="/polls/{{ question.id }}/">{{ question.question_text }}</a></li>
    {% endfor %}
    </ul>
{% else %}
    <p>No polls are available.</p>
{% endif %}

Also, the index of view will be changed accordingly.

polls/views.py

from django.http import HttpResponse
from django.template import loader

from .models import Question


def index(request):
    latest_question_list = Question.objects.order_by('-pub_date')[:5]
    template = loader.get_template('polls/index.html')
    context = {
        'latest_question_list': latest_question_list,
    }
    return HttpResponse(template.render(context, request))

Shortcut: render ()

polls/views.py

from django.shortcuts import render

from .models import Question


def index(request):
    latest_question_list = Question.objects.order_by('-pub_date')[:5]
    context = {'latest_question_list': latest_question_list}
    return render(request, 'polls/index.html', context)

The flow of rendering the series of Templete mentioned above is often used, so it can be omitted in this way.

Sending a 404 error

Change detail to give an error when there is no question with the requested question ID.

polls/views.py

from django.http import Http404
from django.shortcuts import render

from .models import Question
# ...
def detail(request, question_id):
    try:
        question = Question.objects.get(pk=question_id)
    except Question.DoesNotExist:
        raise Http404("Question does not exist")
    return render(request, 'polls/detail.html', {'question': question})

Shortcut: get_object_or_404 ()

polls/views.py

from django.shortcuts import get_object_or_404, render

from .models import Question
# ...
def detail(request, question_id):
    question = get_object_or_404(Question, pk=question_id)
    return render(request, 'polls/detail.html', {'question': question})

Shortcuts are provided because the process of wearing an Http404 when the previous object does not exist is also often used.

There is also a similar shortcut called get_list_or_404 (). This function behaves like get_object_or_404 (), but throws an Http404 if the list is empty.

Use template system

Create a templete corresponding to the detail above.

polls/templates/polls/detail.html

<h1>{{ question.question_text }}</h1>
<ul>
{% for choice in question.choice_set.all %}
    <li>{{ choice.choice_text }}</li>
{% endfor %}
</ul>

Remove hardcoded URL in template

Some of the links were hard coated in polls / index.html. Since the name argument was specified in the path function in polls.urls, replace it there.

This makes it easy to change links when they change.

polls/index.html

- <li><a href="/polls/{{ question.id }}/">{{ question.question_text }}</a></li>
+ <li><a href="{% url 'detail' question.id %}">{{ question.question_text }}</a></li>

(Remove-, add +)

URL namespace

Currently only the polls app exists, but what if there are other apps and the same url name argument is taken there?

In this case, add ʻapp_name to polls / urls.py`.

polls/urls.py

from django.urls import path

from . import views

app_name = 'polls'
urlpatterns = [
    path('', views.index, name='index'),
    path('<int:question_id>/', views.detail, name='detail'),
    path('<int:question_id>/results/', views.results, name='results'),
    path('<int:question_id>/vote/', views.vote, name='vote'),
]

polls / index.html will change accordingly.

polls/templates/polls/index.html

- <li><a href="{% url 'detail' question.id %}">{{ question.question_text }}</a></li>
+ <li><a href="{% url 'polls:detail' question.id %}">{{ question.question_text }}</a></li>