I have been using Django for quite a while but never have I thought of this until now.
Currently, I have a project that contains different user levels. Usually, in my past experience, I only developed systems using Django with only two user levels which are superuser and normal/regular user. So my question is what are the effective ways to present these different user levels in the model/database? Here, I'm going to use a school system as an example and also provide some of my initial thoughts on implementing it.
User levels:
Method #1: Add new tables based on each user level
from django.contrib.auth.models import AbstractUser
from django.db import models
class User(AbstractUser):
user = models.CharfieldField(max_length = 10, unique = True)
class Admin(models.Model):
user = models.OneToOneField(User, on_delete=models.CASCADE, primary_key=True)
class Pricipal(models.Model):
user = models.OneToOneField(User, on_delete=models.CASCADE, primary_key=True)
class Teacher(models.Model):
user = models.OneToOneField(User, on_delete=models.CASCADE, primary_key=True)
class Student(models.Model):
user = models.OneToOneField(User, on_delete=models.CASCADE, primary_key=True)
Method #2: Add additional user types attributes in the User model
from django.contrib.auth.models import AbstractUser
from django.db import models
class User(AbstractUser):
user = models.CharfieldField(max_length = 10, unique = True)
is_superuser = models.BooleanField(default = False)
is_staff = models.BooleanField(default = False)
is_principal = models.BooleanField(default = False)
is_teacher = models.BooleanField(default = False)
is_student = models.BooleanField(default = False
'''
User table in DB:
user | is_superuser | is_staff | is_principal | is_teacher | is_student
'''
My thoughts:
In Method #1, as the built-in User model has two fields, is_staff and is_superuser, Is it possible to implement/change the fields into a SuperUser/Admin table as in the example above? This means that when I create an admin/superuser, I want it to add a new row into the Admin table, instead of adding a new user and updating the user's is_superuser and is_staff fields into 1 in the built-in User model.
In Method #2, the problem with it is that tables with different access privileges are directly connected to it. For example, Salary model (which cannot be accessed by Student user) has a direct link with the User model (contains Student user).
I hope I am able to get some insights and also a proper effective way of implementing this so that to prevent any implementation inconvenience and mistakes in the future. Thank you very much.
One of the methods that I used in several projects is this (pseudo code):
class User(AbstractUser):
ADMIN = 0
PRINCIPLE = 1
TEACHER = 2
STUDENT = 3
USER_LEVEL_CHOICES = (
(ADMIN, "Admin"),
(PRINCIPLE, "Principle"),
(TEACHER, "Teacher"),
(STUDENT, "Student"),
)
user_level = models.IntgerField(choices=USER_LEVEL_CHOICES)
def lvl_decorator():
def check_lvl(func):
def function_wrapper(self, actor, action_on, *args, **kwargs):
if 'action_lvl' not in action_on: # then action_on is user
if actor.user_lvl < action_on.user_lvl:
return True
return False
else: # then action_on is action of some kind for that user (you can add action_lvl to ... and pas them to this wapper)
if actor.user_lvl < action_on.action_lvl:
return True
return False
return function_wrapper
return check_lvl
Then you can write wrapper function with this logic for any action check if action level is bigger than user level e.g.: if someone wants to change superuser password he/she should be logged-in with level-0-user but for changing normal user's password he/she should be level 0, 1. This logic also can be applied to class, functions, etc actions.
Create base class and then add lvl_decorator to it then inherent from it => this keeps your code super clean and prevents further copy paste.
example of what i mean:
def lvl_decorator():
def check_lvl(func):
def function_wrapper(self, actor, action_on, *args, **kwargs):
if 'action_lvl' not in action_on: # then action_on is user
if actor.user_lvl < action_on.user_lvl:
return True
return False
else:
if actor.user_lvl < action_on.action_lvl:
return True
return False
return function_wrapper
return check_lvl
class BaseClass(type):
def __new__(cls, name, bases, local):
for attr in local:
value = local[attr]
if callable(value):
local[attr] = lvl_decorator()
return type.__new__(cls, name, bases, local)
# in other locations like views.py use this sample
class FooViewDjango(object, ApiView): # don't remove object or this won't work, you can use any Django stuff you need to inherent.
__metaclass__ = BaseClass
def baz(self):
print('hora hora')
Use this base class in any where you want.
I think you are in the right path with method #2. It is lighter, and more straightforward.
I would not use a custom "user-like" model for each permission level. Over-complicated, does not scale, and multiply the number of queries, with no very benefit for your problem. Not your UML schema but its content must guarantee your permission requirements.
If the permission levels are not mutual-exclusive :
from django.db import models
from django.contrib.postgres.fields import ArrayField
class User(AbstractUser):
ADMIN = 0
PRINCIPLE = 1
TEACHER = 2
STUDENT = 3
USER_LEVEL_CHOICES = (
(ADMIN, "Admin"),
(PRINCIPLE, "Principle"),
(TEACHER, "Teacher"),
(STUDENT, "Student"),
)
status = ArrayField(
models.IntegerField(choices=USER_LEVEL_CHOICES, blank=True, default=STUDENT),
)
But you need to have a wider reflexion.
I think you are talking about two separate problems : polymorphism, and permissions
Polymorphism is the ability of an object to take on many forms. For a Django model, it can be done with many strategies : OneToOneField -as you mentioned- multi-table inheritance, abstract models, or proxy-models.
Very good resources : this article, and Django doc about model inheritance
This very complex problem all refer to : how much your several forms of a same entity are similar, or different. And which operations are particularly similar or different (data shape, querying, permission, ...etc)
You can choose among several patterns
Model. This is done in Django with the built-in Permission model, that have a ForeignKey to ContentTypeModel instance. Some packages provides this ability, django-guardian for example.rules package provide this kind of architecture.You can create from AbstractUser (a full User model, complete with fields, including is_superuser and is_staff) a Profile and then, once you have the profile, give the chance of users to create other type of profile (Student, Teacher or Principle) which could have functionalities of its own.
For instances, in your models.py
class Profiles(AbstractUser):
date_of_birth = models.DateField(max_length=128, blank=True, null=True, default=None, verbose_name=_(u'Date of birth'))
principle = models.OneToOneField(Principles, null=True, blank=True, verbose_name=_(u'Principles'), on_delete=models.CASCADE)
teacher = models.OneToOneField(Teachers, null=True, blank=True, verbose_name=_(u'Teachers'), on_delete=models.CASCADE)
student = models.OneToOneField(Students, null=True, blank=True, verbose_name=_(u'Students'), on_delete=models.CASCADE)
class Meta:
db_table = 'profiles'
verbose_name = _('Profile')
verbose_name_plural = _('Profiles')
To that model you can add class methods, such as
def is_teacher(self):
if self.teacher:
return True
else:
return False
Then, your Teachers model could look like this
class Teachers(models.Model):
image = models.FileField(upload_to=UploadToPathAndRename(settings.TEACHERS_IMAGES_DIR), blank=True, null=True, verbose_name=_('Teacher logo'))
name = models.CharField(blank=False, null=False, default=None, max_length=255, validators=[MaxLengthValidator(255)], verbose_name=_('Name'))
street = models.CharField( max_length=128, blank=False, null=True, default=None, verbose_name=_('Street'))
created_by = models.ForeignKey('Profiles', null=True, blank=True, on_delete=models.SET_NULL)