ISOM 350

Business Application Development

Mohammad AlMarzouq

Overview of Django Development Process

Django’s Development Model

  • Django is a fullstack MVT web framework.
  • Fullstack because it provides everything we need to build an app, from database handling to templates.
  • It is MVT because its main components are:
  1. Models: To handle data
  2. Views: To handle business logic
  3. Templates: To handle how screens will look

When building apps, we work on models, views, and templates to introduce new features.

Benefits of MVT model

  • Enables collaboration because work on each component is placed in a different file
  • Team members can specialize
    • Data engineers focus on models
    • Backend engineers focus on views
    • Frontend engineers/designers focus on templates
graph TD
A[Setup Project] --> B[Start App for Subproject]
B --> C[Define Data Models]
C -->|Work on Single Feature| D[Create View Function] 
D -->E[Wire URLs to View]
E -->F[Create Templates]
F -->|Refine or Work on Next Feature|D
F -->|Refine or Work on Next Subproject|B

The Steps

1- Project Setup

  • Creates directory structure for project files
  • Specific files for specific functionality
  • Done once at the beginning of the project

Project Setup Methods

  1. (Recommended) Creating a Django Template project in replit.com.
  2. Importing an existing Django project from GitHub.
  3. Using shell you type a command to create a Django project.
Project Structure
Project Structure

Click Run to confirm proper setup

Django Development Server Running
Django Development Server Running

2- Start App or Subproject

  • Code is organized in directories called apps
  • Apps should hold related functionality, for example
    • acounts, cart, blog, store ..etc
  • Project consists of single or multiple apps

Creating an App

  • Using shell, type the following command:
python manage.py startapp blog
Example App Directory
Example App Directory

Adding The App to Our Project

  • In mysite/settings.py update the INSTALLED_APPS list to include our new blog app:
INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'blog',  # Make sure this line is added
]

If you do not perform this step, Django will not see your app!

Do not forget it

3- Define Data Models

  • Data models describe how the data in your project looks like
    • Determined in System Analysis and Design
    • ER-Diagrams

3- Define Data Models

  • Models used to abstractly manage database storage and retrieval
    • Database type and credentials configured in mysite/settings.py
  • Each model will have a corresponding database table that is created automatically

Example models.py File

from django.db import models

class Author(models.Model):
    first_name = models.CharField(max_length=50)
    last_name = models.CharField(max_length=50)
    country = models.CharField(max_length=100)

class Book(models.Model):
    author = models.ForeignKey(
      Author, on_delete=models.CASCADE)
    title = models.CharField(max_length=100)
    release_date = models.DateField()
    num_stars = models.IntegerField()

4- Create View Function

  • Main application server functionality
  • Function for each web app functionality
  • Handle HTTP request and generate HTTP response
    • First argument of the function is always the request
    • Must return an HTTP response

Example views.py File

from django.http import HttpResponse
import datetime

def current_datetime(request):
    now = datetime.datetime.now()
    html = "<html><body>It is now %s.</body></html>" % now
    return HttpResponse(html)

5- Wire URLs

  • Assign a URL path to the view function
  • This step will make the functionality available to the users
  • Done by updating the file mysite/urls.py
    • Called the root urls.py file

Example Root urls.py

from django.urls import include, path
# Import the view function we created
from timeapp.views import current_datetime 

urlpatterns = [
    # Mapp the path time/ to the view function current_datetime
    path('time/', current_datetime, name='current-time'),
]

6- Create Template

  • Templates are text files that are like fstrings
  • The text file is usually an HTML file with some defined slots
  • Allows designers to work independently from developers
  • We insert dynamic data (called context) in these slots to generate a new dynamic web page
  • Can also have basic logic like if and loops

View Function Using Templates

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': latest_question_list}
    return render(request, 'polls/index.html', context)

The polls/index.html File

<html>
    <body>
    {% if latest_question %}
        <ul>
            <li><a href="/polls/{{ latest_question.id }}/">{{ latest_question.question_text }}</a></li>
        </ul>
    {% else %}
        <p>No polls are available.</p>
    {% endif %}
    </body>
</html>

graph TD
A[Setup Project] --> B["Start App for Subproject"]
B --> C["Define Data Models"]
C -->|"Work on Single Feature"| D[Create View Function] 
D -->E["Wire URLs to View"]
E -->F["Create Templates"]
F -->|"Refine or Work on Next Feature"|D
F -->|"Refine or Work on Next Subproject"|B