streamapp.py

#___________myproject/settings.py__________
INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
	'anotherapp',
	'activitystream'
]

#In the project's setting we can see two new apps, one in activitystream, other one is 
#some another app which have an employee module


MIDDLEWARE = [
    'django.middleware.security.SecurityMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.common.CommonMiddleware',
    'django.middleware.csrf.CsrfViewMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
    'django.middleware.clickjacking.XFrameOptionsMiddleware',
    'activitystream.activity_middleware.ActivityMiddleware',
]
#'activitystream.activity_middleware.ActivityMiddleware' is a middleware that detects changes in Employee
#module and takes specified actions
#........................................................


#___________activitystream/models.py__________
from __future__ import unicode_literals
from django.db import models

class Stream(models.Model):
	value=models.CharField(max_length=200)
	
	def __str__(self):
		return self.value

#activity stream app has a single model stream, that has a column named value, where activity log is stored
#as string
#...........................................................


#___________activitystream/activity_middleware.py__________

from anotherapp.models import Employee
from django.db.models.signals import post_save, pre_delete
from django.dispatch import receiver
from datetime import date
from .models import Stream
uname=""

def ActivityMiddleware(get_response):

	def middleware(request):
		global uname
		uname=request.user.username
		response = get_response(request)
		return response

	return middleware
	

@receiver(post_save, sender=Employee)
def save_handler(sender, instance, created, **kwargs):
	if created==True:
		message="Employee {} has been added by {} at {}".format(instance,uname,date.today())
		s=Stream(value=message)
		s.save()
	else:
		message="Employee {} has been updated by {} at {}".format(instance,uname,date.today())
		s=Stream(value=message)
		s.save()

@receiver(pre_delete, sender=Employee)
def delete_handler(sender, instance, **kwargs):
	message="Employee {} has been deleted by {} at {}".format(instance,uname,date.today())
	s=Stream(value=message)
	s.save()

#this middleware detect post_save and pre_delete signal from Employee module of anotherapp, and updates
#Keeps a message about the change in the stream model