Designing the Data Schema

A Poll model stores the main poll questions.

• id: Primary key, auto-incrementing.
• poll_text: The question text, stored as a CharField with a maximum length of 120 characters.
• created_at: The creation timestamp, stored as a DateTimeField.

An Option model stores the choices associated with each poll.

• id: Primary key, auto-incrementing.
• poll: A foreign key linking to the Poll model.
• option_text: The choice text, stored as a CharField with a maximum length of 120 characters.
• votes: An enteger field to count votes, defaulting to 0.

Writing the Model Code

In polls/models.py, define the models:

from django.db import models

class Poll(models.Model):
    poll_text = models.CharField('Poll Question', max_length=120)
    created_at = models.DateTimeField('Created', auto_now_add=True)

    def __str__(self):
        return self.poll_text

class Option(models.Model):
    poll = models.ForeignKey(Poll, verbose_name='Related Poll', on_delete=models.CASCADE)
    option_text = models.CharField('Choice Text', max_length=120)
    votes = models.PositiveIntegerField('Vote Count', default=0)

    def __str__(self):
        return self.option_text

Generating Database Tables from Models

First, activate the polls appliaction by adding it to INSTALLED_APPS in mysite/settings.py:

INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'polls.apps.PollsConfig',
]

Then, create and run the database mgirations from the terminal:

python manage.py makemigrations
python manage.py migrate

Using the Model API

Interact with models in the Django shell:

# Create a new Poll
new_poll = Poll.objects.create(poll_text="What is your preferred IDE?")

# Retrieve a specific Poll by its primary key
poll_one = Poll.objects.get(pk=1)

# Retrieve all Poll objects
all_polls = Poll.objects.all()

# Access a field value
print(poll_one.poll_text)

Setting Up the Django Admin Interface

Create a superuser account:

python manage.py createsuperuser

Register the models in polls/admin.py to manage them via the admin site:

from django.contrib import admin
from .models import Poll, Option

# Inline display for Options within the Poll admin page
class OptionInline(admin.TabularInline):
    model = Option

# Custom admin configuration for the Poll model
class PollAdmin(admin.ModelAdmin):
    inlines = [OptionInline]

admin.site.register(Poll, PollAdmin)
admin.site.register(Option)

Start the development server and navigate to http://127.0.0.1:8000/admin/ to log in.

python manage.py runserver

Implementing Templates

Create a template directory. It can be organized centrally in the project (mysite/templates/polls/) or within the app (polls/templates/polls/). Ensure the template directories are configured in settings.py:

TEMPLATES = [
    {
        'BACKEND': 'django.template.backends.django.DjangoTemplates',
        'DIRS': [os.path.join(BASE_DIR, 'templates')],
        'APP_DIRS': True,
        ...
    },
]

Create a template file, for example polls/templates/polls/list.html, and populate it:

<ul>
{% for item in poll_list %}
    <li>{{ item.poll_text }}</li>
{% endfor %}
</ul>

Creating a View to Render the Template

Update the view in polls/views.py to fetch data and render the template:

from django.shortcuts import render
from .models import Poll

def poll_list(request):
    poll_list = Poll.objects.all()
    context = {'poll_list': poll_list}
    return render(request, 'polls/list.html', context)

This view retrieves all Poll objects, passes them to the template via a context dictionary, and returns the rendered HTML response.