2. Understanding Django’s Architecture: The MTV Pattern.

Django follows the MTV (Model-Template-View) pattern for web development. Here's a breakdown of each component:

Model: Defines your data structure and handles interaction with the database, allowing you to store and retrieve data without writing SQL queries manually.

Template: Responsible for rendering HTML and presenting the data to the user. You write HTML mixed with Django Template Language (DTL) to display dynamic content.

View: Acts as the business logic layer. It connects the Model and Template, handles user requests, interacts with the Model, and returns a response (often HTML rendered from the Template).

How Django's Request-Response Cycle Works:

A user requests a webpage (via a URL).
Django matches the URL to a View.
The View fetches data from the Model and passes it to the Template.
The Template renders the data into HTML and sends it back as a response to the user.

Step 1: Create a New App in Django.
Once you’ve set up Django (as covered in the previous article), let’s create a new app in your project.

Run these commands:

cd mysite
python3 manage.py startapp core

This creates an app named core inside your mysite project. Your file structure should now look like this:

.
├── core
│   ├── admin.py
│   ├── apps.py
│   ├── __init__.py
│   ├── migrations
│   │   └── __init__.py
│   ├── models.py
│   ├── tests.py
│   └── views.py
├── db.sqlite3
├── manage.py
└── mysite
    ├── asgi.py
    ├── __init__.py
    ├── settings.py
    ├── urls.py
    └── wsgi.py

Step 2: Register Your App in the Settings File.
To make Django aware of the new app, you need to add it to the 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',
    'core',  # add this line
]

Step 3: Create a Basic View.
Let’s create a simple view that returns a “Hello, World!” message.

Open views.py inside the core app and add the following code:

from django.http import HttpResponse

def learn(request):
    return HttpResponse("Hello, World!")

Step 4: Map URLs to the View.
To access this view via a URL, you need to map it in the core/urls.py file. Create this file if it doesn’t exist and add the following:

from django.urls import path
from . import views

urlpatterns = [
    path('learn/', views.learn, name='learn'),
]

Next, include the core app's URLs in the main mysite/urls.py file:

from django.contrib import admin
from django.urls import include, path

urlpatterns = [
    path('admin/', admin.site.urls),
    path('core/', include('core.urls')),  # include the core app URLs
]

Now, if you run the server and visit http://127.0.0.1:8000/core/learn/, you should see "Hello, World!" displayed.
Step 5: Create and Render a Template

from django.shortcuts import render

def learn(request):
    context = {'name': 'Django'}
    return render(request, 'hello.html', context)

This view now passes a variable (name) to a template called hello.html.
Step 6: Create a Template Directory and HTML File.
In your core app, create a templates folder and an hello.html file:

mkdir core/templates
touch core/templates/hello.html

Inside hello.html, add the following HTML code

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Hello Template</title>
</head>
<body>
    <h1>Hello, {{ name }}!</h1>
</body>
</html>

When you visit the learn URL again, you should now see "Hello, Django!" in the browser.

Step 7: Create a Basic Model.
Let’s create a simple Post model to store blog posts.

In core/models.py, add the following code:

from django.db import models

class Post(models.Model):
    title = models.CharField(max_length=100)
    content = models.TextField()

    def __str__(self):
        return self.title

This Postmodel has two fields: titleand content. The__str__ method ensures that the Post objects are displayed with their titles in the Django admin or shell

Step 8: Apply the Model to the Database.
To create the corresponding table in the database, run these commands:

python3 manage.py makemigrations
python3 manage.py migrate

Django will now create a database table for the Post model.

By following these steps, you've successfully created a basic Django app with a model, view, and template. You can now expand upon this foundation by adding more features, such as handling user input, improving the design, and making the app more interactive.

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2. Understanding Django’s Architecture: The MTV Pattern.

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