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How to access object count in template using model manager?

I have a model which creates Memo objects. I would like to use a custom Model Manager's posted method to return the total number of Memo objects - then use this number within a template. I am trying to keep as much of my code as possible within my Models and Model Managers and less within my Views as I read that this was a best practice in 'Two Scoops of Django'.
In the shell I can get the number of memos as such:
>>> from memos.models import Memo
>>> Memo.objects.all()
<QuerySet [<Memo: Test Memo 2>, <Memo: Test Memo 1>]>
>>> Memo.objects.all().count()
2
This is what my Model and Model Manager look like:
class MemoManager(models.Manager):
use_for_related_fields = True
def posted(self):
return self.count()
class Memo(models.Model):
title = models.CharField(max_length=100)
content = models.TextField()
date_time = models.DateTimeField(default=timezone.now)
author = models.ForeignKey(User, on_delete=models.CASCADE)
objects = MemoManager()
def __str__(self):
return self.title
def get_absolute_url(self):
return reverse('memos-detail', kwargs={'pk': self.pk})
I know this is clearly the wrong way to do it but I have confused myself here. So how do I use my Model Manager to get the count of objects and use it in a template like: {{ objects.all.count }}?
P.S. I see other posts that show how to do this within the view but as stated I am trying not to use the view. Is using the view required? I also understand my posted method is written incorrectly.

I'm sorry but you have misinterpreted what was written in TSD. The Lean View Fat Model is meant to keep code which pertains to 'business logic' out of the views, and certain model specific things. A request should be handled by a view. So when you want to load a template, you must first have a GET request to your app.
A view function should be written such that Validation of POST data or the Creation of a new object in DB or Querying/Filtering for GET requests should be handled in the corresponding serializer/model/model manager.
What should be happening while you want to load your template.
Have a url for the template that you have created and a view function mapped for it
In the view function you should render said template and pass the necessary data inside the context.
To keep in line with the Lean View Fat Model style, if you want to get a Queryset of of Memo's but only those which have their is_deleted fields set to False, you can overwrite the model manager get_queryset() method for Memo model.
If you want to create a new Memo with a POST request, you can handle
the creation using a ModelForm!
Hope this clears things up!
EDIT:
How to pass a context to a template, in your case the memo count.
def random_memo_view(request):
context = {'memo_count': Memo.posted()}
return render(request, 'template.html', context=context)
RE-EDIT
I just checked that you were using DetailView. In this case follow this from the django docs.
Class Based Views: Adding Extra Context

Django multi model best practice

Basically what I'm trying to achieve is a multi-model django app where different models take advantage of the same views. For example I've got the models 'Car' 'Make' 'Model' etc and I want to build a single view to perform the same task for each, such as add, delete and edit, so I don't have to create a seperate view for add car, ass make etc. I've built a ModelForm and Model object for each and would want to create a blank object when adding and a pre-populated form object when editing (through the form instance arg), with objects being determined via url parameters.
Where I'm stuck is that I'm not sure what the best way to so this is. At the moment I'm using a load of if statements to return the desired object or form based on parameters I'm giving it, which get's a bit tricky when different forms need specifying and whether they need an instance or not. Although this seems to be far from the most efficient way of achieving this.
Django seems to have functions to cover most repetitive tasks, is there some magic I'm missing here?
edit - Here's an example of what I'm doing with the arguments I'm passing into the url:
def edit_object(request, object, id):
if(object==car):
form = carForm(instance = Car.objects.get(pk=id)
return render(request, 'template.html', {'form':form})

What about using Class Based Views? Using CBVs is the best way in Django to make reusable code. For this example maybe it can be a little longer than function based views, but when the project grows up it makes the difference. Also remember "Explicit is better than implicit".
urls.py
# Edit
url(r'^car/edit/(?P<pk>\d+)/$', EditCar.as_view(), name='edit-car'),
url(r'^make/edit/(?P<pk>\d+)/$', EditMake.as_view(), name='edit-make'),
# Delete
url(r'^car/delete/(?P<pk>\d+)/$', DeleteCar.as_view(), name='delete-car'),
url(r'^make/delete/(?P<pk>\d+)/$', DeleteMake.as_view(), name='delete-make'),
views.py
class EditSomethingMixin(object):
"""Use Mixins to reuse common behavior"""
template_name = 'template-edit.html'
class EditCar(EditSomethingMixin, UpdateView):
model = Car
form_class = CarForm
class EditMake(EditSomethingMixin, UpdateView):
model = Make
form_class = MakeForm
class DeleteSomethingMixin(object):
"""Use Mixins to reuse common behavior"""
template_name = 'template-delete.html'
class DeleteCar(DeleteSomethingMixin, DeleteView):
model = Car
class DeleteMake(DeleteSomethingMixin, DeleteView):
model = Make

Just pass your class and form as args to the method then call them in the code.
def edit_object(request, model_cls, model_form, id):
form = model_form(instance = model_cls.objects.get(pk=id)
return render(request, 'template.html', {'form':form})
then just pass in the correct classes and forms in your view methods
def edit_car(request,id):
return edit_object(request, Car, CarForm, id)
each method knows what classes to pass, so you eliminate the if statements.

urls.py
url(r'^car/delete/(?<pk>\d+)/', edit, {'model': Car})
url(r'^make/delete/(?<pk>\d+)/', edit, {'model': Make})
views.py
def edit(request, id, model):
model.objects.get(id=id).delete()

Django Admin - how to prevent deletion of some of the inlines

I have 2 models - for example, Book and Page.
Page has a foreign key to Book.
Each page can be marked as "was_read" (boolean), and I want to prevent deleting pages that were read (in the admin).
In the admin - Page is an inline within Book (I don't want Page to be a standalone model in the admin).
My problem - how can I achieve the behavior that a page that was read won't be deleted?
I'm using Django 1.4 and I tried several options:
Override "delete" to throw a ValidationError - the problem is that the admin doesn't "catch" the ValidationError on delete and you get an error page, so this is not a good option.
Override in the PageAdminInline the method - has_delete_permission - the problem here -it's per type so either I allow to delete all pages or I don't.
Are there any other good options without overriding the html code?
Thanks,
Li

The solution is as follows (no HTML code is required):
In admin file, define the following:
from django.forms.models import BaseInlineFormSet
class PageFormSet(BaseInlineFormSet):
def clean(self):
super(PageFormSet, self).clean()
for form in self.forms:
if not hasattr(form, 'cleaned_data'):
continue
data = form.cleaned_data
curr_instance = form.instance
was_read = curr_instance.was_read
if (data.get('DELETE') and was_read):
raise ValidationError('Error')
class PageInline(admin.TabularInline):
model = Page
formset = PageFormSet

You could disable the delete checkbox UI-wise by creating your own custom
formset for the inline model, and set can_delete to False there. For
example:
from django.forms import models
from django.contrib import admin
class MyInline(models.BaseInlineFormSet):
def __init__(self, *args, **kwargs):
super(MyInline, self).__init__(*args, **kwargs)
self.can_delete = False
class InlineOptions(admin.StackedInline):
model = InlineModel
formset = MyInline
class MainOptions(admin.ModelAdmin):
model = MainModel
inlines = [InlineOptions]

Another technique is to disable the DELETE checkbox.
This solution has the benefit of giving visual feedback to the user because she will see a grayed-out checkbox.
from django.forms.models import BaseInlineFormSet
class MyInlineFormSet(BaseInlineFormSet):
def add_fields(self, form, index):
super().add_fields(form, index)
if some_criteria_to_prevent_deletion:
form.fields['DELETE'].disabled = True
This code leverages the Field.disabled property added in Django 1.9. As the documentation says, "even if a user tampers with the field’s value submitted to the server, it will be ignored in favor of the value from the form’s initial data," so you don't need to add more code to prevent deletion.

In your inline, you can add the flag can_delete=False
EG:
class MyInline(admin.TabularInline):
model = models.mymodel
can_delete = False

I found a very easy solution to quietly avoid unwanted deletion of some inlines. You can just override delete_forms property method.
This works not just on admin, but on regular inlines too.
from django.forms.models import BaseInlineFormSet
class MyInlineFormSet(BaseInlineFormSet):
#property
def deleted_forms(self):
deleted_forms = super(MyInlineFormSet, self).deleted_forms
for i, form in enumerate(deleted_forms):
# Use form.instance to access object instance if needed
if some_criteria_to_prevent_deletion:
deleted_forms.pop(i)
return deleted_forms

Django custom registration fields

I'm becoming increasingly bewildered by the range of answers on offer to the seemingly simple problem of adding custom fields to the django-registration register form/flow. This should be a default, documented aspect of the package (not to sound ungrateful, just that it is such a well-equipped package), but solutions to the problem are dizzying.
Can anyone give me the most simple solution to getting UserProfile model data included in the default registration register page?
Update:
I eventually used Django Registration's own signals to give me this hacky fix. It is particularly ugly because, I had to use try on the POST attribute dealing with my Boolean since I found that the checkbox returned nothing if left empty.
Would appreciate any advice on improving this, or best practice.
My app / models.py
from registration.signals import user_registered
from django.dispatch import receiver
class UserProfile(models.Model):
user = models.OneToOneField(User)
event_commitments = models.ManyToManyField(Event, null=True, blank=True)
receive_email = models.BooleanField(default=True)
#receiver(user_registered)
def registration_active_receive_email(sender, user, request, **kwargs):
user_id = user.userprofile.id
user = UserProfile.objects.get(pk=user_id)
try:
if request.POST['receive_email']:
pass
except:
user.receive_email = False
user.save()
Registration app / forms.py
class RegistrationForm(forms.Form):
# default fields here, followed by my custom field below
receive_email = forms.BooleanField(initial=True, required=False)
Thanks

What you have looks like a workable approach.
I've looked through the django-registration code, and based on the following comments in the register view I've come up with another solution. I'm not totally sure this is cleaner, but if you aren't a fan of signals this is good. This also provides a much easier avenue if you intend to make more customizations.
# from registration.views.register:
"""
...
2. The form to use for account registration will be obtained by
calling the backend's ``get_form_class()`` method, passing the
``HttpRequest``. To override this, see the list of optional
arguments for this view (below).
3. If valid, the form's ``cleaned_data`` will be passed (as
keyword arguments, and along with the ``HttpRequest``) to the
backend's ``register()`` method, which should return the new
``User`` object.
...
"""
You could create a custom backend and override those mentioned methods:
# extend the provided form to get those fields and the validation for free
class CustomRegistrationForm(registration.forms.RegistrationForm):
receive_email = forms.BooleanField(initial=True, required=False)
# again, extend the default backend to get most of the functionality for free
class RegistrationBackend(registration.backends.default.DefaultBackend):
# provide your custom form to the registration view
def get_form_class(self, request):
return CustomRegistrationForm
# replace what you're doing in the signal handler here
def register(self, request, **kwargs):
new_user = super(RegistrationBackend, self).register(request, **kwargs)
# do your profile stuff here
# the form's cleaned_data is available as kwargs to this method
profile = new_user.userprofile
# use .get as a more concise alternative to try/except around [] access
profile.receive_email = kwargs.get('receive_email', False)
profile.save()
return new_user
To use the custom backend, you can then provide separate urls. Before including the default urls, write 2 confs that point at your custom backend. Urls are tested in the order defined, so if you define these two before including the defaults, these two will capture before the default ones are tested.
url(r'^accounts/activate/(?P<activation_key>\w+)/$',
activate,
{'backend': 'my.app.RegistrationBackend'},
name='registration_activate'),
url(r'^accounts/register/$',
register,
{'backend': 'my.app.RegistrationBackend'},
name='registration_register'),
url(r'^accounts/', include('registration.backends.default.urls')),
The docs actually describe all this, but they aren't particularly accessible (no readthedocs). They are all included in the project, and I was browsing them here.

I eventually used Django Registration's own signals to give me this fix.
I will clean up the try/except flow at some point. dokkaebi also points out above that I might be able to assess the request.GET parameters for when a checkbox is left empty.
My app / models.py
from registration.signals import user_registered
from django.dispatch import receiver
class UserProfile(models.Model):
user = models.OneToOneField(User)
event_commitments = models.ManyToManyField(Event, null=True, blank=True)
receive_email = models.BooleanField(default=True)
#receiver(user_registered)
def registration_active_receive_email(sender, user, request, **kwargs):
user_id = user.userprofile.id
user = UserProfile.objects.get(pk=user_id)
try:
if request.POST['receive_email']:
pass
except:
user.receive_email = False
user.save()
Registration app / forms.py
class RegistrationForm(forms.Form):
# default fields here, followed by my custom field below
receive_email = forms.BooleanField(initial=True, required=False)

Django: multiple models in one template using forms [closed]

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I'm building a support ticket tracking app and have a few models I'd like to create from one page. Tickets belong to a Customer via a ForeignKey. Notes belong to Tickets via a ForeignKey as well. I'd like to have the option of selecting a Customer (that's a whole separate project) OR creating a new Customer, then creating a Ticket and finally creating a Note assigned to the new ticket.
Since I'm fairly new to Django, I tend to work iteratively, trying out new features each time. I've played with ModelForms but I want to hide some of the fields and do some complex validation. It seems like the level of control I'm looking for either requires formsets or doing everything by hand, complete with a tedious, hand-coded template page, which I'm trying to avoid.
Is there some lovely feature I'm missing? Does someone have a good reference or example for using formsets? I spent a whole weekend on the API docs for them and I'm still clueless. Is it a design issue if I break down and hand-code everything?

This really isn't too hard to implement with ModelForms. So lets say you have Forms A, B, and C. You print out each of the forms and the page and now you need to handle the POST.
if request.POST():
a_valid = formA.is_valid()
b_valid = formB.is_valid()
c_valid = formC.is_valid()
# we do this since 'and' short circuits and we want to check to whole page for form errors
if a_valid and b_valid and c_valid:
a = formA.save()
b = formB.save(commit=False)
c = formC.save(commit=False)
b.foreignkeytoA = a
b.save()
c.foreignkeytoB = b
c.save()
Here are the docs for custom validation.

I just was in about the same situation a day ago, and here are my 2 cents:
1) I found arguably the shortest and most concise demonstration of multiple model entry in single form here: http://collingrady.wordpress.com/2008/02/18/editing-multiple-objects-in-django-with-newforms/ .
In a nutshell: Make a form for each model, submit them both to template in a single <form>, using prefix keyarg and have the view handle validation. If there is dependency, just make sure you save the "parent"
model before dependant, and use parent's ID for foreign key before commiting save of "child" model. The link has the demo.
2) Maybe formsets can be beaten into doing this, but as far as I delved in, formsets are primarily for entering multiples of the same model, which may be optionally tied to another model/models by foreign keys. However, there seem to be no default option for entering more than one model's data and that's not what formset seems to be meant for.

I very recently had the some problem and just figured out how to do this.
Assuming you have three classes, Primary, B, C and that B,C have a foreign key to primary
class PrimaryForm(ModelForm):
class Meta:
model = Primary
class BForm(ModelForm):
class Meta:
model = B
exclude = ('primary',)
class CForm(ModelForm):
class Meta:
model = C
exclude = ('primary',)
def generateView(request):
if request.method == 'POST': # If the form has been submitted...
primary_form = PrimaryForm(request.POST, prefix = "primary")
b_form = BForm(request.POST, prefix = "b")
c_form = CForm(request.POST, prefix = "c")
if primary_form.is_valid() and b_form.is_valid() and c_form.is_valid(): # All validation rules pass
print "all validation passed"
primary = primary_form.save()
b_form.cleaned_data["primary"] = primary
b = b_form.save()
c_form.cleaned_data["primary"] = primary
c = c_form.save()
return HttpResponseRedirect("/viewer/%s/" % (primary.name))
else:
print "failed"
else:
primary_form = PrimaryForm(prefix = "primary")
b_form = BForm(prefix = "b")
c_form = Form(prefix = "c")
return render_to_response('multi_model.html', {
'primary_form': primary_form,
'b_form': b_form,
'c_form': c_form,
})
This method should allow you to do whatever validation you require, as well as generating all three objects on the same page. I have also used javascript and hidden fields to allow the generation of multiple B,C objects on the same page.

The MultiModelForm from django-betterforms is a convenient wrapper to do what is described in Gnudiff's answer. It wraps regular ModelForms in a single class which is transparently (at least for basic usage) used as a single form. I've copied an example from their docs below.
# forms.py
from django import forms
from django.contrib.auth import get_user_model
from betterforms.multiform import MultiModelForm
from .models import UserProfile
User = get_user_model()
class UserEditForm(forms.ModelForm):
class Meta:
fields = ('email',)
class UserProfileForm(forms.ModelForm):
class Meta:
fields = ('favorite_color',)
class UserEditMultiForm(MultiModelForm):
form_classes = {
'user': UserEditForm,
'profile': UserProfileForm,
}
# views.py
from django.views.generic import UpdateView
from django.core.urlresolvers import reverse_lazy
from django.shortcuts import redirect
from django.contrib.auth import get_user_model
from .forms import UserEditMultiForm
User = get_user_model()
class UserSignupView(UpdateView):
model = User
form_class = UserEditMultiForm
success_url = reverse_lazy('home')
def get_form_kwargs(self):
kwargs = super(UserSignupView, self).get_form_kwargs()
kwargs.update(instance={
'user': self.object,
'profile': self.object.profile,
})
return kwargs

I currently have a workaround functional (it passes my unit tests). It is a good solution to my opinion when you only want to add a limited number of fields from other models.
Am I missing something here ?
class UserProfileForm(ModelForm):
def __init__(self, instance=None, *args, **kwargs):
# Add these fields from the user object
_fields = ('first_name', 'last_name', 'email',)
# Retrieve initial (current) data from the user object
_initial = model_to_dict(instance.user, _fields) if instance is not None else {}
# Pass the initial data to the base
super(UserProfileForm, self).__init__(initial=_initial, instance=instance, *args, **kwargs)
# Retrieve the fields from the user model and update the fields with it
self.fields.update(fields_for_model(User, _fields))
class Meta:
model = UserProfile
exclude = ('user',)
def save(self, *args, **kwargs):
u = self.instance.user
u.first_name = self.cleaned_data['first_name']
u.last_name = self.cleaned_data['last_name']
u.email = self.cleaned_data['email']
u.save()
profile = super(UserProfileForm, self).save(*args,**kwargs)
return profile

"I want to hide some of the fields and do some complex validation."
I start with the built-in admin interface.
Build the ModelForm to show the desired fields.
Extend the Form with the validation rules within the form. Usually this is a clean method.
Be sure this part works reasonably well.
Once this is done, you can move away from the built-in admin interface.
Then you can fool around with multiple, partially related forms on a single web page. This is a bunch of template stuff to present all the forms on a single page.
Then you have to write the view function to read and validated the various form things and do the various object saves().
"Is it a design issue if I break down and hand-code everything?" No, it's just a lot of time for not much benefit.

According to Django documentation, inline formsets are for this purpose:
"Inline formsets is a small abstraction layer on top of model formsets. These simplify the case of working with related objects via a foreign key".
See https://docs.djangoproject.com/en/dev/topics/forms/modelforms/#inline-formsets