Custom permissions in Django - Step-by-Step Execution

Concept Flow - Custom permissions

Define Permission Class

↓

Implement has_permission()

↓

Attach Permission to View

↓

Request Received

↓

Call has_permission()

Yes No↓

Allow Access

This flow shows how a custom permission class is defined, attached to a view, and used to allow or deny access based on logic in has_permission.

Execution Sample

Django

from rest_framework.permissions import BasePermission

class IsOwner(BasePermission):
    def has_permission(self, request, view):
        return request.user.is_authenticated and request.user.is_owner

Defines a custom permission that allows access only if the user is authenticated and is an owner.

Execution Table

Step	Action	Input (request.user)	has_permission Result	Access Outcome
1	Request with user.is_authenticated=True, user.is_owner=True	user.is_authenticated=True, user.is_owner=True	True	Access Allowed
2	Request with user.is_authenticated=True, user.is_owner=False	user.is_authenticated=True, user.is_owner=False	False	Access Denied
3	Request with user.is_authenticated=False, user.is_owner=True	user.is_authenticated=False, user.is_owner=True	False	Access Denied
4	Request with user.is_authenticated=False, user.is_owner=False	user.is_authenticated=False, user.is_owner=False	False	Access Denied

💡 Access is allowed only when has_permission returns True; otherwise, access is denied.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4
request.user.is_authenticated	N/A	True	True	False	False
request.user.is_owner	N/A	True	False	True	False
has_permission result	N/A	True	False	False	False
Access Outcome	N/A	Allowed	Denied	Denied	Denied

Key Moments - 2 Insights

Why does access get denied even if the user is authenticated?

Because the has_permission method requires both is_authenticated and is_owner to be True. See execution_table row 2 where is_owner is False, so access is denied.

What happens if the user is not authenticated but is_owner is True?

Access is denied because has_permission checks both conditions. See execution_table row 3 where is_authenticated is False, so access is denied.

Visual Quiz - 3 Questions

Look at the execution table, what is the has_permission result at step 2?

A True

B False

C None

D Error

💡 Hint

Check the 'has_permission Result' column at step 2 in the execution_table.

At which step is access allowed?

A Step 3

B Step 2

C Step 1

D Step 4

💡 Hint

Look at the 'Access Outcome' column in the execution_table.

If we change has_permission to only check is_authenticated, how would step 4 change?

A Access Denied

B Access Allowed

C Error occurs

D No change

💡 Hint

Refer to variable_tracker for step 4 and consider only is_authenticated condition.

Concept Snapshot

Custom permissions in Django REST Framework:
- Create a class inheriting BasePermission
- Override has_permission(self, request, view)
- Return True to allow access, False to deny
- Attach permission class to views
- Controls access based on request.user or other logic

Full Transcript

Custom permissions in Django REST Framework let you control who can access your views. You create a class that inherits from BasePermission and write a has_permission method. This method checks the request, usually the user, and returns True or False. If True, the user can access the view; if False, access is denied. You then attach this permission class to your view. The execution table shows different user states and whether access is allowed or denied based on the permission logic.