I have models like this:
class Devices(models.Model):
name = models.CharField(max_length=255, blank=True)
uniqueid = models.CharField(db_column='uniqueid'.lower(), max_length=255, blank=True) # Field name made lowercase.
latestposition = models.ForeignKey('Positions', db_column='latestPosition_id'.lower(), blank=True, null=True) # Field name made lowercase.
class Meta:
db_table = 'devices'
verbose_name = 'Devices'
verbose_name_plural = verbose_name
def __unicode__(self):
return '%s' %(self.name)
# Call the signal to create user device when the device is created.
dispatcher.connect(save_user_device, signal=post_save, sender=Devices)
class UsersDevices(models.Model):
user = models.ForeignKey(settings.AUTH_USER_MODEL)
devices = models.ForeignKey('Devices')
class Meta:
db_table = 'users_devices'
verbose_name = 'User Devices'
verbose_name_plural = verbose_name
def __unicode__(self):
return '%s %s' %(self.user, self.devices)
When the Devices is created, I want to create users devices. user field in the UsersDevices would be signed in user who created device and devices would be the device that was just created.
def save_user_device(sender, instance, **kwargs):
## Problem is here
instance.UsersDevices.create( )
How can I create a UsersDevices using this signal with the user instance and device instance
You don't really need signals in this case. Overwrite the save() method of the model:
def save(self, *args, **kwargs):
# Call the original save function to actually save the model:
super(Devices, self).save(*args, **kwargs)
# Now this model is saved, so we can create the UsersDevices
UserDevices(user=get_user_from_somewhere(), devices=self).save()
See the documentation for more information about overwriting the save() method:
https://docs.djangoproject.com/en/1.7/topics/db/models/#overriding-model-methods
It is better to redefine save method of Devices model for this purpose. But if you want to use signals it might be done like this:
def save_user_device(sender, instance, **kwargs):
## Problem is here
UsersDevices.create(devices=instance, user=instance.user)
In this case you have to add 'user' field to Devices model.
And small tip: you should give names to models singularly, plural names is bad style.
Related
2 Classes involved in question class Appointment and class Service
appointmentApp.models class Service
class Service(models.Model):
service_name = models.CharField(max_length=15, blank=False)
service_time = models.IntegerField(blank=False)
def __str__(self):
return self.service_name
class Meta:
verbose_name_plural = "Services"
appointmentApp/models.py class Appointment
class Appointment(models.Model):
service_chosen = models.ManyToManyField(Service, blank=False)
total_time = models.IntegerField(blank=False, null=False, default=0)
#will add up the amount of time needed for each service
def save(self, *args, **kwargs):
self.total_time += Service.objects.all().aggregate(total_time=Sum('service_time'))['total_time']
super(Appointment, self).save(*args, **kwargs)
def __str__(self):
return self.client_dog_name
Services are chosen through a multiplechoice field and on save the service_chosen's service_time are added up
but what my save function is doing instead is adding up all the existing service.service_time instead of the ones selected, why is this happening?
ManyToManyFields are saved after the containing instance is saved, you need to create a signal handler to perform this update on m2m_changed
from django.db.models.signals import m2m_changed
class Appointment(models.Model):
...
def service_chosen_changed(sender, instance=None, action=None, **kwargs):
if action == 'post_add':
instance.total_time = instance.service_chosen.aggregate(total_time=Sum('service_time'))['total_time']
instance.save()
m2m_changed.connect(service_chosen_changed, sender=Appointment.service_chosen.through)
I am testing forms and nesting models in django. In my Project a Person can enter departure, arrival (city names) and choose a weekly day (Mon-Fri). Maybe he drives every “Tuesday” from Amsterdam to Paris. I wanted this constellation to be unique – just for fun. So If another user enters the same route the relation should be linked to the same Car.object.
Models.py
class Person(models.Model):
name = models.CharField(max_length=255, blank=False, unique=True)
route = models.ManyToManyField('Car')
def __str__(self):
return self.name
class Car(models.Model):
name = models.CharField(max_length=255, blank=False, unique=True)
weekdays = models.ForeignKey('Week', null=True, blank=False, on_delete=models.SET_NULL)
departure = models.CharField(max_length=255, blank=False)
arrival = models.CharField(max_length=255, blank=False)
class Meta:
unique_together = ['weekdays', 'departure', 'arrival'] # --- Unique combination
def __str__(self):
return self.name
class Week(models.Model):
day = models.CharField(max_length=255, blank=False, unique=True)
def __str__(self):
return self.day
views.py
class RouteCreateView(CreateView):
model = Person
template_name ="testa/create_route.html"
form_class = RouteForm
success_url = reverse_lazy('testa:testa_home')
def form_valid(self, form):
return super().form_valid(form)
forms.py
class RouteForm(forms.ModelForm):
# --- apply ChoiceField
day = forms.ModelChoiceField(queryset=None)
car_name = forms.CharField()
departure = forms.CharField()
arrival = forms.CharField()
class Meta:
model = Person
fields = [
'name'
]
def __init__(self, *args, **kwargs):
super(RouteForm, self).__init__(*args, **kwargs)
self.fields['day'].queryset = Week.objects.all()
def save(self, commit=True):
personData = super().save(commit)
data = self.cleaned_data
carData = Car(name=data['car_name'], weekdays=data['day'], departure=data['departure'], arrival=data['arrival'])
if commit:
carData.save()
personData.route.add(carData) # --- save m2m relation
return personData
If i enter two times for example „“Tuesday” from Amsterdam to Paris “ then an Error Message appears obviously, this error message (it´s german), telling me I have a double entry / Key.
Question
So my save()Method does not work because I need some kind of logic, so that Django takes the existing car.object or creates a new - if it is not a double entry. But I do not know where to start? The easiest way would be to get some kind of response from my model meta option Car.unique_together so "if it´s an “double-key error” then take the existing object". Is there a way to fetch the response? And what kind of Values it would be, only errors, could not find any hint in the doc? Or should I try some logic with exists()
That was my kind of idea / approach of a new save() 😊
def save(self, commit=True):
personData = super().save(commit)
data = self.cleaned_data
carData = Car(name=data['car_name'], weekdays=data['day'], departure=data['departure'], arrival=data['arrival'])
if commit:
# Check if database sends unique_together response
# if yes
if Car.Meta.unique_together is True:
getAlternative = Car.object.get(Meta.unique_together) # --- get the object which already exist
personData.route.add(getAlternative) # --- save m2m relation
# if not
else:
carData.save() # --- save object
personData.route.add(carData) # --- save m2m relation
return personData
obviously i get a error message: type object 'Car' has no attribute
'Meta'
Theres get_or_create for such use case: https://docs.djangoproject.com/en/2.2/ref/models/querysets/#get-or-create
...
car, created = Car.objects.get_or_create(
weekdays=data['day'],
departure=data['departure'],
arrival=data['arrival'],
defaults = dict(name=data['car_name']),
)
personData.route.add(car)
...
Obviously given name gets ignored if another car with same weekdas, departure, arrival has been found.
I suggest to put the code for creating the car and adding the route in a transaction.atomic() https://docs.djangoproject.com/en/2.2/topics/db/transactions/#django.db.transaction.atomic
I have two models (Post and Display). Both have Datetime-auto fields. My problem is that i want to update all display objects related to a post, once a post is updated.
I have read here that you could override one models save method, but all the examples are About updating the model with the foreign key in it and then call the save method of the other model. In my case it's the other way arround. How can i do this ?
class Post(models.Model):
title = models.CharField(max_length=40)
content = models.TextField(max_length=300)
date_posted = models.DateTimeField(auto_now=True)
author = models.ForeignKey(User, on_delete=models.CASCADE)
rooms = models.ManyToManyField(Room, related_name='roomposts', through='Display')
def __str__(self):
return self.title
def get_absolute_url(self):
return "/post/{}/".format(self.pk)
class Display(models.Model):
post = models.ForeignKey(Post, on_delete=models.CASCADE)
room = models.ForeignKey(Room, on_delete=models.CASCADE)
isdisplayed = models.BooleanField(default=0)
date_posted = models.DateTimeField(auto_now=True)
def __str__(self):
return str(self.isdisplayed)
i want to update the date_posted of all related Display-objects once their related post is changed. I do not know if overriding the save-method works here.
in this case you should have a look at django's reverse foreign key documentation
https://docs.djangoproject.com/en/2.2/topics/db/queries/#following-relationships-backward
in your case you can override the save method on your Post model
def save(self, *args, **kwargs):
super().save(*args, **kwargs)
#either: this excutes many sql statments
for display in self.display_set.all():
display.save()
#or faster: this excute only one sql statements,
#but note that this does not call Display.save
self.display_set.all().update(date_posted=self.date_posted)
The name display_set can be changed using the related_name option
in Display, you can change it:
post = models.ForeignKey(Post, on_delete=models.CASCADE, related_name='displays')
Then, instead of using self.display_set in your code, you can use self.displays
Overriding save method works, but that's not were you should go, imo.
What you need is signals:
#receiver(post_save, sender=Post)
def update_displays_on_post_save(sender, instance, **kwargs):
if kwargs.get('created') is False: # This means you have updated the post
# do smth with instance.display_set
Usually it goes into signals.py.
Also you need to include this in you AppConfig
def ready(self):
from . import signals # noqa
I write the code to edit the list of users which belong to a team. For this I create a form, as below:
class Organization(models.Model):
name = models.CharField(blank=False, verbose_name=_("Name"), help_text=_('Organization Name'), max_length=256)
class Team(models.Model):
organization = models.ForeignKey('Organization')
name = models.CharField(blank=False, verbose_name=_("Name"), help_text=_('Team Name'), max_length=256)
users = models.ManyToManyField('User', related_name='teams')
def __str__(self):
return self.name
class TeamUsersForm(forms.ModelForm):
class Meta:
model = Team
fields = ['users']
users = forms.ModelMultipleChoiceField(queryset=User.objects.filter(request.user.organization), required=False)
def clean_users(self):
users = self.cleaned_data['users']
if users.exclude(organization=request.user.organization):
raise ValidationError(_("Cannot add user from another organization"))
return users
The code above should look into request value to determine the current organization and restrict display and model store only to users from the same organization.
But the above code cannot work, because the value of request is not known at class loading time.
What do you suggest to do?
I thought of two variants:
create a local (to a function) class like the above class TeamUsersForm
dismiss using Django forms for this altogether and use more low-level API
Overide the __init__ of the TeamUsersForm and access request there.
class TeamUsersForm(forms.ModelForm):
def __init__(self, *args, **kwargs):
self.request = kwargs.pop('request')
super().__init__(*args, **kwargs)
self.fields['users'] = forms.ModelMultipleChoiceField(queryset=User.objects.filter(self.request.user.organization), required=False)
This implies that when you instantiate your form, you should it this way:
# somewhere in your views.py, probably
f = TeamUsersForm(request.POST, request=request)
I am trying to create a Model and ModelForm with "name" and "client" fields that have the following cleaning and validation characteristics. I can manage each individual requirement but can't seem get them to work together.
An authenticated user can enter a name for an Item
Item is saved with the name and forced to the client that is associated with the user account.
Name is cleaned via ' '.join(name.strip().split())
Name is validated so that (cleaned_name.lower(),client) is unique
EG: If "FOO BAR" exists in the user's associated client, user would get an error if they enter "foo bar"
It is a fairly simple model:
class Item(BaseModel):
class Meta:
unique_together = (("client", "name"),)
client = models.ForeignKey(Client,related_name='items',null=True,blank=False)
name = models.CharField(max_length=64, null=False, blank=False)
def clean_name(self):
return ' '.join(self.cleaned_data['name'].strip().split())
All item creates/updates are done via Django REST Framework:
class ItemSerializer(serializers.HyperlinkedModelSerializer):
class Meta:
model = Item
fields = ('id','name')
def create(self,validated_data):
item = Item.objects.create(name=validated_data['name'],client=self.context['request'].user.client)
item.save()
return item
I would prefer as much of the logic in the Model as possible (eg, not use SQL to create indexes), but could push some of the validation to the serializer if need be.
Tx.
I ended up with the following. The only caveat is that I have to include a name_slug field to store for sorting purposes.
models.py
class Item(BaseModel):
class Meta:
db_table = 'item'
ordering = ['name_slug']
# relations
client = models.ForeignKey(Client,related_name='items',null=True,blank=False)
# attributes
name = models.CharField(max_length=64, null=False, blank=False)
name_slug = models.CharField(max_length=64, null=False, blank=True)
def clean(self):
self.name = ' '.join(self.name.strip().split())
if Item.objects.filter(client=self.client,name__iexact=self.name).count() > 0:
raise ValidationError({'name': 'Name already exists. Please enter a different name'})
def save(self, *args, **kwargs):
self.name_slug = '-'.join(self.name.split()).lower()
super(Item, self).save(*args, **kwargs)
serializers.py
class ItemSerializer(serializers.HyperlinkedModelSerializer):
class Meta:
model = Item
fields = ('id','name','name_slug')
read_only_fields = ('name_slug',)
def validate(self, attrs):
attrs['client'] = self.context['request'].user.client
instance = Item(**attrs)
instance.clean()
return { k: getattr(instance,k) for k in attrs.keys()}