I want to create a new variable which is always available like how the 'user' variable works.
Here is my myapp/context_processors.py
def patient_selected(request):
print(hasattr(request, 'patient_selected_id'))
print( 'patient_selected_id' in locals())
print( 'patient_selected_id' in globals())
if not hasattr(request, 'patient_selected_id'):
request.patient_selected_id = 0
return {"patient_selected_id": 0}
The problem is, it always prints 'false'. It seems like I cannot add an attribute to the request, nor create a variable constantly available. BTW, I have added this context_processors.py to settings. Here is my setting:
TEMPLATES = [
{
'BACKEND': 'django.template.backends.django.DjangoTemplates',
'DIRS': [],
'APP_DIRS': True,
'OPTIONS': {
'context_processors': [
'django.template.context_processors.debug',
'django.template.context_processors.request',
'django.contrib.auth.context_processors.auth',
'django.contrib.messages.context_processors.messages',
'hrs.context_processors.patient_selected',
],
},
},
]
EDIT: After reading source codes, it seems like the user variable is not actually created once and live forever. The Middleware and context_processor add a variable user for every request, and this 'user' is actually pulled from session.
My original design is: Once a patient is selected, all following pages will be about this patient. Thus, I would like to make this patient's id always available. Instead of pass this id all around, I want to save it(somewhere) once and always available until another patient is selected.
However now, considering the complexity of user variable, I may give up the fancy way. Simply put this id as a parameter in every request url should be easier.
Django does that with middleware [Django-doc]. In fact setting the .user attribute is done with middleware as well. Indeed, you can see this in the AuthenticationMiddleware [GitHub]:
class AuthenticationMiddleware(MiddlewareMixin): def process_request(self, request): assert hasattr(request, 'session'), ( "The Django authentication middleware requires session middleware " "to be installed. Edit your MIDDLEWARE%s setting to insert " "'django.contrib.sessions.middleware.SessionMiddleware' before " "'django.contrib.auth.middleware.AuthenticationMiddleware'." ) % ("_CLASSES" if settings.MIDDLEWARE is None else "") request.user = SimpleLazyObject(lambda: get_user(request))
If you remove the 'django.contrib.auth.middleware.AuthenticationMiddleware' string from the MIDDLEWARE setting [Django-doc], then the request.user will no longer be set.
You can thus implement your own middleware. For example with:
# app/middleware.py
from django.utils.deprecation import MiddlewareMixin
class PatientSelectIdMiddleware(MiddlewareMixin):
def process_request(self, request):
if not hasattr(request, 'patient_selected_id'):
request.patient_selected_id = 0Next you need to add the 'app.PatientSelectIdMiddleware' middleware to the MIDDLEWARE setting.
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