ISOM 350

Business Application Development

Mohammad AlMarzouq

Improved URLs

URL Paths

It’s a good idea to make them readable
Can be static:

/blog/posts

Or Dynamic (known as URL Patterns):

/blog/post/10
/blog/post/234
/profile/khaled
/profile/ahmed

Defining URL Paths

Done in mysite/urls.py
We add Paths to the urlpatterns list
Each Path links a URL path to a view function:

urlpatterns = [ 
    path('test/', test_view),   
    path('blog/post', blog_posts),   
]

Remember to import the view functions!

Defining Dynamic Paths

Place them in the urlpatterns list
Example dynamic paths:

path('profile/<str:name>/', user_profile),
path('blog/post/<slug:slug>/', view_post_by_slug),
path('blog/post/<int:id>/', view_post_by_id),
path('blog/post/<int:year>/<int:month>/', view_posts_in_month),

Defining Variable in URL Paths

The syntax:

<data_type:variable_name>

Just place it in the part that you would like to vary in the URL path

View Functions with Dynamic Paths

For every variable in the URL path, the linked view function must have a matching argument that match the variable name
For example, the following path:

path('profile/<str:name>/', user_profile),

Must be matched with the following view function:

def user_profile(request, name):

Another Matching Example

The following path:

path('blog/post/<int:year>/<int:month>/', view_posts_in_month),

Must be matched with the following view function:

def view_posts_in_month(request, year, month):

Improved URL Organization

Look at the admin urls:

path('admin/', admin.site.urls),

What is admin.site.urls?
It is not a view function, but the url paths for the admin interface
Similarly, we can define URL paths in our app directory

Defining URLS Inside an APP

Create a urls.py inside the blog app
in the root urls.py (mysite/urls.py):
- import the include function from django.urls
- use include to point to the urls in your app

The Improved Root urls.py

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

urlpatterns = [
    path('admin/', admin.site.urls),   
    path('blog/', include('blog.urls')),
]

This is telling Django that our paths can be found in the blog app in the file named urls.py

The blog prefix

One important thing to keep in mind, that all the blog app urls will start with /blog
because of this line:

path('blog/', include('blog.urls')),

If the URL path starts with /blog/, then the rest of the path can be processed according to blog/urls.py

blog/urls.py

from . import views
from django.urls import path

urlpatterns = [
    path('', views.post_list),
    path('<slug:slug>/', views.display_post),
]

Notice we do not execute the function using ()

Why Are URL Path Variable Important?

Allows for selection of specific items or ranges in our data
Considered a user input method

How Can URLs Be Used for Input?

Let’s improve our test_view function to:
1. Define the urls in blog/urls.py
2. Set the name of the person to greet from url, /greet/mohammad will result in the message “hello mohammad”

Root urls.py:

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

urlpatterns = [
    path('admin/', admin.site.urls),   
    path('blog/', include('blog.urls')),
]

blog/urls.py

from . import views
from django.urls import path

urlpatterns = [
    path('greet/<str:name>', views.test_view),
]

blog/views.py

def test_view(request, name):
  data = {}
  data["name"] = name
  return render(request, 'test.html', context=data)

blog/templates/test.html

<html>
  <body>
  <h1>Hello {{ name }}!</h1>
</html>

Now how can you access the view from the browser?

The correct path is:

/blog/greet/your-name-here

As you change the name part in the path, so will the message in the page

This understanding of URLs will be important for the next part of working with data.
Please read the URL dispatcher documentation for more information.

Final Note on URLs

It is good practice to give unique names for URLs in Django
Will allow you to avoid hard-coding urls in your web app
An excellent explanation is provided in the django documentation