edc-registration

The model RegisteredSubject is used by the Edc as the master subject registration table. Only one record may exist per individual. The table has space for PII so typically a RegisteredSubject instance is created or updated on completion of the informed consent. As always, PII in the Edc is encrypted at rest using django-crypto-field.

RegisteredSubjectModelMixin

Declare RegisteredSubject in your app using the RegisteredSubjectModelMixin, for example:

class RegisteredSubject(RegisteredSubjectModelMixin, BaseUuidModel):
    class Meta:
        app_label = 'my_app'

then in edc_registration AppConfig specify the app_label = 'my_app' so that other modules in the Edc can find the model class. (Note: The model_name is assumed to always be RegisteredSubject).

Other modules can find the model class by accessing the AppConfig:

>>> from django.apps import apps as django_apps
>>> RegisteredSubject = django_apps.get_app_config('edc_registration').model
>>> RegisteredSubject.objects.get(subject_identifier='12345678-9')
<RegisteredSubject: 12345678-9>

UpdatesOrCreatesRegistrationModelMixin

RegisteredSubject is never edited directly by the user. Instead some other model with the needed attributes is used as a proxy. To have a model perform the task of creating or updating RegisteredSubject, declare it with the UpdatesOrCreatesRegistrationModelMixin.

For example, a model, SubjectEligibility or a screening model creates or updates a RegisteredSubject without a subject identifier then a model such as the SubjectConsent in tests.models, also creates or updates a subject's RegisteredSubject instance on save. For this to happen, both models are declared with the UpdatesOrCreatesRegistrationModelMixin:

class SubjectEligibility(UniqueSubjectIdentifierModelMixin, UpdatesOrCreatesRegistrationModelMixin, BaseUuidModel):

screening_identifier = models.CharField(
    max_length=36,
    null=True,
    unique=True)

@property
def registration_unique_field(self):
    return 'screening_identifier'

def update_subject_identifier_on_save(self):
    """Overridden to not set the subject identifier on save.
    """
    if not self.subject_identifier:
        self.subject_identifier = self.subject_identifier_as_pk.hex
        self.subject_identifier_aka = self.subject_identifier_as_pk.hex
    return self.subject_identifier

class SubjectConsent(ConsentModelMixin, UpdatesOrCreatesRegistrationModelMixin, CreateAppointmentsMixin,
                     IdentityFieldsMixin, ReviewFieldsMixin, PersonalFieldsMixin,
                     CitizenFieldsMixin, VulnerabilityFieldsMixin, BaseUuidModel):
                     
	@property
    def registration_unique_field(self):
        return 'screening_identifier'

    class Meta:
        app_label = 'my_app'

The property registration_unique_field returns a model attribute that is used to set a registration identifier on RegisteredSubject.

A subject's RegisteredSubject instance is created and updated in a post_save signal. As mentioned, it is never edited directly by the user.

For the signal to be registered you need to add the AppConfig to your INSTALLED_APPS:

INSTALLED_APPS = (
    ....
    'edc_registration.apps.AppConfig',
    ....
    )

However, since RegisteredSubject is not a model in edc_registration, you should subclass AppConfig instead, for example:

from django.apps import AppConfig as DjangoAppConfig
from edc_registration.apps import AppConfig as EdcRegistrationAppConfigParent

class AppConfig(DjangoAppConfig):
    name = 'my_app'

class EdcRegistrationAppConfig(EdcRegistrationAppConfigParent):
    app_label = 'my_app'

and update settings accordingly:

INSTALLED_APPS = (
    ....
    'my_app.apps.EdcRegistrationAppConfig',
    'my_app.apps.AppConfig',
    ....
    )

RegisteredSubjectMixin

Since the app_label of the model class RegisteredSubject is not known when the models classes are loaded, it is difficult to include the class as a foreign key. As a work around, use the RegisteredSubjectMixin. When this mixin is declared on your model, the subject_identifier field is added to the model and verified against RegisteredSubject on each save.

The subject_identifier field is added with editable=False. You must provide the correct subject identifier programmatically or the model will raise an RegisteredSubject.DoesNotExist exception on save.