Wednesday, December 30, 2015

Working with Django signals

I have a custom users schema in Django for work with roles or users type, creating an application named userprofile which will be or will setup my custom user model.

In my settings.py I have the following configuration:

INSTALLED_APPS = [          ...      'userprofile',  ]  #Custom model Users  AUTH_USER_MODEL = 'userprofile.User'


I customize my User class (userprofile/models.py) that inherit of the AbstractUser class for add some fields to my User model due to my requirements demanded me.

I also create these another models for roles/profile users (MedicalProfile, PatientProfile, PhysiotherapistProfile) with their own fields or attributes


In addition MedicalProfile, PatientProfile, PhysiotherapistProfile have a OneToOneField relationship with my custom model/class User so:


from __future__ import unicode_literals    from django.conf import settings  from django.contrib.auth.models import AbstractUser  from django.db import models    #from django.contrib.auth import get_user_model      from django.dispatch import receiver  from django.db.models.signals import post_save      # Extending Django's default User  # https://docs.djangoproject.com/en/1.9/topics/auth/customizing/#extending-django-s-default-user  # We inherit from AbstractUser class to add some fields/attibutes to our user model  # https://github.com/django/django/blob/master/django/contrib/auth/models.py#L297  # Differentes between AbstractUser and AbstractBaseUser  # http://stackoverflow.com/questions/21514354/difference-between-abstractuser-and-abstractbaseuser-in-django  class User(AbstractUser):      is_medical = models.BooleanField(default=False)      is_physiotherapist = models.BooleanField(default=False)      is_patient = models.BooleanField(default=False)      slug = models.SlugField(max_length=100, blank=True)      photo = models.ImageField(upload_to='avatars', null = True, blank = True)          # We get the profiles user according with their type      def get_medical_profile(self):          medical_profile = None          if hasattr(self, 'medicalprofile'):              medical_profile=self.medicalprofile          return medical_profile        def get_patient_profile(self):          patient_profile = None          if hasattr(self, 'patientprofile'):              patient_profile = self.patientprofile          return patient_profile        def get_physiotherapist_profile(self):          physiotherapist_profile = None          if hasattr(self, 'physiotherapistprofile'):              physiotherapist_profile = self.physiotherapistprofile          return physiotherapist_profile        # We redefine the attributes (create db_table attribute) in class Meta to say to Django      # that users will save in the same table that the Django default user model      # https://github.com/django/django/blob/master/django/contrib/auth/models.py#L343      class Meta:            db_table = 'auth_user'    class MedicalProfile(models.Model):      user = models.OneToOneField(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)      #active = models.BooleanField(default=True)      name = models.CharField(max_length=64)      class PatientProfile(models.Model):      user = models.OneToOneField(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)      #active = models.BooleanField(default=True)      name = models.CharField(max_length=64)      class PhysiotherapistProfile(models.Model):      user = models.OneToOneField(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)      #active = models.BooleanField(default=True)      name = models.CharField(max_length=64)      """  So we're defined a signal for the User model, that is triggered every time a User instance is saved    The arguments used in the create_profile_for_new_user  are:     sender: the User model class     created: a boolean indicating if a new User has been created     instance: the User instance being saved  """  @receiver(post_save, sender=settings.AUTH_USER_MODEL)  #def create_profile_for_new_user(sender, instance, created, **kwargs):  def create_profile_for_new_user(sender, instance, created, **kwargs):      user = instance      # ----------------- Begin debug----------------------      import ipdb      #ipdb.set_trace()      #------------------------      if created:          #ipdb.set_trace()          if user.is_medical:              ipdb.set_trace()              profile=MedicalProfile(user=instance)              profile.save()    """  This signal checks if a new instance of the User model has been created,  and if true, it creates a Profile instance with using the new user instance.  """


My Question

I want to focus my question in relation about of the post_save signal operation, this mean in the create_profile_for_new_user() method:


@receiver(post_save, sender=settings.AUTH_USER_MODEL)  def create_profile_for_new_user(sender, instance, created, **kwargs):      user = instance      # ----------------- Begin debug----------------------      import ipdb      #------------------------      if created:          if user.is_medical:              ipdb.set_trace()              profile=MedicalProfile(user=instance)              profile.save()


I want, each that an user is created, automatically (by post_save signal action) be created their profile (MedicalProfile, PatientProfile, PhysiotherapistProfile) according to if their field checked (is_medical, is_patient, is_physiotherapist) at the User class (same black image presented above)

The inconvenient that I have is with my signal, and it's the following:

  • When I create an user via django admin, indicating that this user is medical (have the is_medical field/attribute checked in the user admin form) in my MedicalProfile model, their profile instance not is saved or don't created

I have been checking the situation through ipdb basic debug functions and I think so that when I create the user the compiler or the steps don't arrive to the section when I check if my user is medical (if user.is_medical code line) such as follow:


1. I've placed a debug point initially of this way:


In the code section in where the user instance that has been created is sent


enter image description here



  1. 2. I create a user via django admin

I go to my Django admin and I create a new user and when press click in "Save" (first moment to user create): 


enter image description here



3. When I press "Save" button, the debug point enter to action


Then, I check the value of the variables that accord to my function which I am applying the signal are defined until the moment and they are inside the debug process. They are:

  • sendercreatedinstance (this mean, the parameters of the function)
  • user, that is the same instance variable

enter image description here


The above,denote that the parameters are arriving. All is O.K for the moment.



  1. 4. Moving the debug

  2. Then, I perform the debug a few more below in the code (red square in the following figure) and I analyze the following:

enter image description here


It's true the sender, instance and created parameters are arriving and when check for the is_medical attribute (boolean) which depend that the profile be saved in MedicalProfile model, I get this:


enter image description here



My attribute is_medical have the boolean value as False and I think that I can understand it, because we know that the user creation is divided in two sequentials phases in the django admin



  • The first phase when I allocate username and password

enter image description here

  • And the second phase when I enter the other fields or attributes in the creation of the that same user.

And, is in that same phase in which I tell to Django that my user will be or will have the medical profile, checking the is_medical checkbox attribute


enter image description here




I think that when the user is saved in the first phase (I allocate only username and password) the is_medical checkbox not yet is setup (checked) and this is the reason by which their value is False

It's right?

  1. 5. If I placed a few more below the set_trace() point debug such as follow in the figure (red square):

enter image description here


In this point, ipdb do not enter in action, my debug is not reached or does not work.


The signal action that is doing is create the new User, but not create the profile for the user, in this case, the MedicalProfile beacuse I checked the is_medical checkbox when I was create the user. Just create the user and nothing more ...



I think that the is_medical attribute never is True, despite that I checked via admin django form, ant these it's the condition for that my user instance be saved in MedicalProfile model. :(


All this, carry me to the following question:


What alternatives can I have for solve this situation and when I create an user, their profile instance be saved (MedicalProfile, PhysiotherapistProfile, PatientProfile) depending of the attribute checkbo/field (is_medical, is_physiotherapist , is_patient) that I choose?


I bring to all my apologies before, in case of the my question do not be suited or appropriated with the stackoverflow philosophy or by the extense of my question.


The reason that it's extense is that I want give all details for get an answer


Any orientation I will be grateful and will be appreciated




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