Permission required decorator in Django - Step-by-Step Execution

Concept Flow - Permission required decorator

Request comes in

↓

Decorator checks user permissions

↓

Run view

↓

Response sent back

The decorator checks if the user has the needed permission before running the view. If yes, the view runs; if no, a 403 error is returned.

Execution Sample

Django

@permission_required('app.view_item')
def my_view(request):
    return HttpResponse('Allowed')

This code checks if the user has 'app.view_item' permission before running my_view.

Execution Table

Step	Action	User Permission Check	Result	View Execution	Response
1	Request received	Check if user has 'app.view_item'	User has permission	View runs	HttpResponse with 'Allowed'
2	Request received	Check if user has 'app.view_item'	User lacks permission	View blocked	HttpResponse 403 Forbidden

💡 Execution stops after permission check fails or view returns response.

Variable Tracker

Variable	Start	After Check	Final
user.has_perm('app.view_item')	Unknown	True or False	True or False

Key Moments - 2 Insights

Why does the view not run if the user lacks permission?

Because the decorator checks permissions first (see execution_table step 2) and returns 403 before calling the view.

What happens if the user has the permission?

The decorator lets the view run normally (see execution_table step 1), so the user gets the expected response.

Visual Quiz - 3 Questions

Look at the execution table, what response is returned if the user lacks permission?

A HttpResponse with 'Allowed'

B HttpResponse 403 Forbidden

C Redirect to login page

D Empty response

💡 Hint

Check execution_table row 2, 'Response' column.

At which step does the view function actually run?

A Step 2

B Before step 1

C Step 1

D After step 2

💡 Hint

See execution_table row 1, 'View Execution' column.

If the decorator is removed, what changes in the execution table?

A Permission check is skipped, view always runs

B 403 Forbidden is always returned

C Request is blocked before view

D Response is delayed

💡 Hint

Without decorator, no permission check step exists.

Concept Snapshot

Permission required decorator syntax:
@permission_required('app.permission_name')
Checks if user has permission before running view.
If yes, view runs and returns response.
If no, returns 403 Forbidden response.
Prevents unauthorized access simply.

Full Transcript

The permission required decorator in Django checks if the user has a specific permission before allowing a view to run. When a request comes in, the decorator first checks the user's permissions. If the user has the required permission, the view function executes and returns its response. If the user lacks the permission, the decorator stops the view from running and returns a 403 Forbidden response instead. This protects views from unauthorized access. The execution table shows two main paths: one where the user has permission and the view runs, and one where the user does not and gets blocked. The variable tracker follows the permission check result. Key moments include understanding why the view does not run without permission and what happens when permission is granted. The visual quiz tests understanding of these steps and outcomes. This decorator is a simple way to secure views in Django.