I have a model.
class Exam(models.Model):
Examname = models.CharField(null=False, blank=False, max_length=255)
def save(self, *args, **kwargs):
self.Examname = self.Examname.lower()
return super(Exam, self).save(*args, **kwargs)
class Meta:
unique_together = ["Examname"]
def __str__(self):
return self.Examname
Examname must be case insensitive in order to avoid the duplicate data. I converted all to small letters and stored. But it is not detecting the duplicate data. for example if i insert External as Examname it is storing as external but other name if i give as external then only it detects as dulicate data. External or eXternal or any atleast one capital letter is there it is not detecting as duplicate data but stored as small letters
First of all, if regno should store numbers as well as characters, do not use FloatField but for example CharField
If you want avoid case sensitivity issues, you may want for example decide to always store values low case when saving your object as follow:
def save(self, *args, **kwargs):
self.regno = self.regno.lower()
super(Show, self).save(*args, **kwargs)
If you need to preserve case, the alternative option would be to duplicate lowcase content in a secondary CharField. Which can be automated in the save method.
If you try to insert a duplicate value, django will throw an IntegrityError, which should be handled.
class MyModel(models.Model):
mytextfield = models.CharField()
lowcase_textfield = models.CharField(unique=True)
def save(self, *args, **kwargs):
self.lowcase_textfield = self.mytextfield.lower()
try:
super(MyModel, self).save(*args, **kwargs)
except IntegrityError as e:
# INSERT YOUR EXCEPTION HANDLING HERE
pass
Related
I have a model where the authenticated user is a FK field. I'm running into problems calling self.partial_update via the UpdateModelMixin as user field cannot be null.
I believe this occurs when it fails to update and falls back to creating. How do I pass user=self.request.user as a parameter only when creating?
I tried modifying the request.data dict but it's apparently immutable
Edit: Fields user and a are sort of like a composite primary key for the other fields so I've made them read_only in the serializer. The API never deals with the model_id pk.
class MView(generics.UpdateAPIView, mixins.UpdateModelMixin):
def get_object(self):
a_check = self.request.data.get('a') #Other validity checks but I removed it for simplicity
if a_check:
return models.M.objects.filter(user=self.request.user,a=a).first()
def put(self, request, *args, **kwargs):
try:
#request.data.update({'user':self.request.user})
print(request.data)
return self.partial_update(request, *args, **kwargs)
class M(models.Model):
user = models.ForeignKey(CustomUser,on_delete='CASCADE')
...
class MSerializer(serializers.ModelSerializer):
class Meta:
model = models.M
fields = ('a','b','c')
read_only_fields = ('user', 'a')
One possible solution is to overwrite the update function from mixins.UpdateModelMixin lifeclycle. check update function link
def update(self, request, *args, **kwargs):
partial = kwargs.pop('partial', False)
instance = self.get_object()
serializer = self.get_serializer(instance, data={**request.data, user: self.request.user}, partial=partial)
serializer.is_valid(raise_exception=True)
self.perform_update(serializer)
if getattr(instance, '_prefetched_objects_cache', None):
# If 'prefetch_related' has been applied to a queryset, we need to
# forcibly invalidate the prefetch cache on the instance.
instance._prefetched_objects_cache = {}
return Response(serializer.data)
Ended up solving it by overwriting the create/update methods in the serializer
def create(self, validated_data):
instance = M.objects.create(user=self.context['request'].user,
**validated_data)
return instance
DRF will use the editable=False on a field to default the Serializer to read-only. This is a very helpful / safe default that I take advantage of (ie I won't forget to set the Serializer to read-only). That being said once I have set editable=False is there any way to then force the Django admin to allow editing one of those fields?
Presumably the admin is a super user and I do want him to be able to change the fields value but fore safety I want the default Serializer logic to be read only.
UPDATE
I don't actually need to be able to edit the field as much as "set-it" when I create the object.
You are going about this the wrong way.
Your models should be the most pure implementation of the things you are modelling. If something about a model is fixed (for example a creation date) it shouldn't be editable in the model, if its mutable, then leave as editable in the model.
Otherwise, in the future you (or someone else) might be stuck wondering why a field which is set to editable=False is some how being changed. Especially as the documentation states:
If False, the field will not be displayed in the admin or any other ModelForm. They are also skipped during model validation.
If you have one view in which it shouldn't be editable (such as in the API), then override it there.
If you have multiple serilaizers for a model, instead make an abstract serializer with a read_only_fields set and then subclass that. For example:
class AbstractFooSerializer(serializers.ModelSerializer):
class Meta:
model = Foo
read_only_fields = ('bar',)
class MainFooSerializer(AbstractFooSerializer):
pass
class DifferentFooSerializer(AbstractFooSerializer):
pass
If you really, really want to use editable=False, but allow the item to be edited in the Admin site only on creation you have an up hill battle.
Probably the best approach would be to reimplement the AdminForm you are using for the Admin
So instead of:
class FooAdmin(admin.ModelAdmin):
Use:
class FooAdmin(admin.ModelAdmin):
form = MySpecialForm
Then declare the form:
class MySpecialForm(forms.Model):
def __init__(self, *args, **kwargs):
self.is_new = False
if kwargs.get('instance',None) is None:
# There is no instance, thus its a new item
self.is_new = True
self.fields['one_time_field'] = forms.CharField() # Or what have you.
super(MySpecialForm, self).__init__(*args, **kwargs)
def save(self, commit=True):
instance = super(MySpecialForm, self).save(commit)
if self.is_new:
instance.your_one_time_only_field = self.one_time_field
instance.save()
return instance
Note: you will need to manually add a field and save each readonly field that you want to do this for. This may or may not be 100% functional.
For those who want to allow editing of a non-editabled field only during creation (no instance.pk, yet):
# models.py
class Entity(Model):
name = CharField(max_length=200, unique=True, null=False, blank=False, editable=False)
# admin.py
#register(Entity)
class EntityAdmin(ModelAdmin):
def get_readonly_fields(self, request, obj=None):
if obj: # This is the case when obj is already created i.e. it's an edit
return ['id', 'name']
else:
return []
# this override prevents that the new_name field shows up in the change form if it's not a creation
def get_form(self, request, obj=None, **kwargs):
orig_self_form = self.form
if not obj:
self.form = CreateEntityForm
result = super().get_form(request, obj=obj, **kwargs)
self.form = orig_self_form
return result
# forms.py
class CreateEntityForm(ModelForm):
new_name = CharField(max_length=200, min_length=2, label='Name', required=True)
def clean_new_name(self):
code = self.cleaned_data['new_name']
# validate uniqueness - if you need
exists = Entity.objects.filter(name=code).first()
if exists:
raise ValidationError('Entity with this name already exists: {}', exists)
return name
def save(self, commit=True):
if self.instance.pk:
raise NotImplementedError('Editing of existing Entity is not allowed!')
self.instance.name = self.cleaned_data['new_name'].upper()
return super().save(commit)
class Meta:
model = Entity
fields = ['new_name']
exclude = ['id', 'name']
I have a users share model something like below:
class Share( models.Model ):
sharer = models.ForeignKey(User, verbose_name=_("Sharer"), related_name='sharer')
receiver = models.ForeignKey(User, verbose_name=_("Receiver"), related_name='receiver')
class Meta:
unique_together = ( ("sharer", "receiver"), ("receiver", "sharer") )
I want to save a single object for sharer(S) and receiver(R) (order doesn't matters R-S or S-R). but above unique_together will not fulfil this; Suppose R-S is in database and then if I save S-R I will not get validation for this. For this I have written custom unique validation for Share model.
def validate_unique(
self, *args, **kwargs):
super(Share, self).validate_unique(*args, **kwargs)
if self.__class__.objects.filter( Q(sharer=self.receiver, receiver=self.sharer) ).exists():
raise ValidationError(
{
NON_FIELD_ERRORS:
('Share with same sharer and receiver already exists.',)
}
)
def save(self, *args, **kwargs):
# custom unique validate
self.validate_unique()
super(Share, self).save(*args, **kwargs)
This method works fine in normal use.
Problem:
I have an matching algorithm which gets a share's and a receiver's requests and saves Share object(either S-R or R-S) then send them response(share object) at almost same time. As I am checking duplication with query(no database level) it takes time, so at the end I have 2 Objects S-R and R-S.
I want some solution for this that for a sharer S and a receiver R I can only save single share object, either S-R or R-S else get some validation error(like IntegrityError of databse).
Django=1.4, Database=Postgresql
You probably could solve this with postgresql's indexes on expressions but here is another way:
class Share( models.Model ):
sharer = models.ForeignKey(User)
receiver = models.ForeignKey(User), related_name='receiver')
key = models.CharField(max_length=64, unique=True)
def save(self, *args, **kwargs):
self.key = "{}.{}".format(*sorted([self.sharer_id, self.receiver_id]))
super(Share, self).save(*args, **kwargs)
But it obviously wouldn't work if you change values with QuerySet.update method. You also could look at django-denorm, it solves this with triggers.
I have a Django app where users submit orders for payment. Clearly, security is important. I want to minimise the amount of code that I have to write, to avoid introducing any security holes, and ease maintenance.
The model is simple:
class Order(models.Model):
user = models.ForeignKey(User)
created = models.DateTimeField()
paid = models.DateTimeField(null=True, blank=True)
items = models.ManyToManyField(Item)
I'm using a CreateView to create instances of Order:
class OrderView(CreateView):
model = Order
form_class = OrderForm
I want to enforce values for certain fields in those instances. For example, I want the instance user field set to the current logged-in user. I don't want any possibility that the user can change the value of this field, so I don't want it to appear in the form at all. Therefore I use a custom ModelForm to remove these fields from the form:
class OrderForm(forms.ModelForm):
class Meta:
model = Order
# For security, we control exactly which fields are placed
# in the form, rather than excluding some:
fields = ('items',)
Now I want the newly created Order instances to have the user field set to the current logged-in user. I can't find any documentation about what is the best way to do this.
(A) I can override the form's save() method to modify the object before saving, but it feels like this code doesn't belong in the form, which doesn't know anything about the user field. I also don't have access to the request here, which I'd need to determine the current user. But it might look like this:
class OrderForm(forms.ModelForm):
def save(self, commit=True):
instance = super(OrderForm, self).save(commit=False)
instance.user = get_request_magic().user
if commit:
instance.save()
return instance
(B) I can override the view's form_valid method to save the object with commit=False, like a class-based version of this question. But I can't call the superclass method directly, because it saves the object with no way to disable commit, so I have to manually skip a generation of form_valid which is nasty. Apart from that complaint, this does look like the best way I've found so far:
class OrderView(CreateView):
def form_valid(self, form):
self.object = form.save(commit=False)
self.object.user = self.request.user
self.object.save()
return super(ModelFormMixin, self).form_valid(form)
(C) I could write a replacement for CreateView that adds a hook to allow objects to be changed before saving them. But that feels like more boilerplate and duplication.
(D) I can't provide an initial value, because there's no form field to put it in, so it will be ignored.
Any other ideas? If (B) the best option, is there any way around the hacky way of manually specifying which superclass' form_valid method I want to call?
Django user Charettes answered the question for me:
You can achieve this by overriding form_valid:
class OrderCreateViewMixin(CreateView):
def form_valid(self, form):
form.instance.user = request.user
return super(OrderCreateViewMixin, self).form_valid(form)
Which pointed me towards the right part of the documentation:
class AuthorCreate(CreateView):
form_class = AuthorForm
model = Author
def form_valid(self, form):
form.instance.created_by = self.request.user
return super(AuthorCreate, self).form_valid(form)
This is definitely the simplest and cleanest answer I've found so far. It doesn't require modifying the form in any way, although it does directly access its instance member which is a bit ugly. However, at least it's officially documented, so it's unlikely to break.
There are probably multiple approaches to this. I would do this:
Create a constructor in your form which takes the request:
def __init__(self, *args, **kwargs):
request = kwargs.pop('request', None)
super(OrderForm, self).__init__(*args, **kwargs)
self.request = request
When creating your form for POST processing, instantiate it as follows:
form = OrderForm(data=request.POST, request=request)
Now, in your save() method, you have access to the user on the request by referencing self.request.user and can set it accordingly on your model.
The way I've gone about handling this situation with CBVs, is to pass in an unsaved instance of the model to the form. This is how I've done it:
class OrderView(CreateView):
def get_form_kwargs(self):
self.object = Order(user=self.request.user)
return super(OrderView, self).get_form_kwargs()
Both CreateView and UpdateView will add instance to the form kwargs, setting it to the value of self.object.
The only other way, besides what you've already mentioned, is to construct your view class from the same elements that CreateView does, and then change the get and post methods to populate self.object there. I've done that when I have needed a lot of create views in my project:
class OrderView(SingleObjectTemplateResponseMixin, ModelFormMixin, ProcessFormView):
template_name_suffix = '_form'
def get(self, request, *args, **kwargs):
self.object = Order(user=request.user)
return super(OrderView, self).get(request, *args, **kwargs)
def post(self, request, *args, **kwargs):
self.object = Order(user=request.user)
return super(OrderView, self).post(request, *args, **kwargs)
Here is a more generalized version to be reused: https://gist.github.com/4439975
Suppose my models.py is like so:
class Character(models.Model):
name = models.CharField(max_length=255)
is_the_chosen_one = models.BooleanField()
I want only one of my Character instances to have is_the_chosen_one == True and all others to have is_the_chosen_one == False . How can I best ensure this uniqueness constraint is respected?
Top marks to answers that take into account the importance of respecting the constraint at the database, model and (admin) form levels!
Whenever I've needed to accomplish this task, what I've done is override the save method for the model and have it check if any other model has the flag already set (and turn it off).
class Character(models.Model):
name = models.CharField(max_length=255)
is_the_chosen_one = models.BooleanField()
def save(self, *args, **kwargs):
if self.is_the_chosen_one:
try:
temp = Character.objects.get(is_the_chosen_one=True)
if self != temp:
temp.is_the_chosen_one = False
temp.save()
except Character.DoesNotExist:
pass
super(Character, self).save(*args, **kwargs)
I'd override the save method of the model and if you've set the boolean to True, make sure all others are set to False.
from django.db import transaction
class Character(models.Model):
name = models.CharField(max_length=255)
is_the_chosen_one = models.BooleanField()
def save(self, *args, **kwargs):
if not self.is_the_chosen_one:
return super(Character, self).save(*args, **kwargs)
with transaction.atomic():
Character.objects.filter(
is_the_chosen_one=True).update(is_the_chosen_one=False)
return super(Character, self).save(*args, **kwargs)
I tried editing the similar answer by Adam, but it was rejected for changing too much of the original answer. This way is more succinct and efficient as the checking of other entries is done in a single query.
It is simpler to add this kind of constraint to your model
after Django version 2.2. You can directly use UniqueConstraint.condition. Django Docs
Just override your models class Meta like this:
class Meta:
constraints = [
UniqueConstraint(fields=['is_the_chosen_one'], condition=Q(is_the_chosen_one=True), name='unique_is_the_chosen_one')
]
Instead of using custom model cleaning/saving, I created a custom field overriding the pre_save method on django.db.models.BooleanField. Instead of raising an error if another field was True, I made all other fields False if it was True. Also instead of raising an error if the field was False and no other field was True, I saved it the field as True
fields.py
from django.db.models import BooleanField
class UniqueBooleanField(BooleanField):
def pre_save(self, model_instance, add):
objects = model_instance.__class__.objects
# If True then set all others as False
if getattr(model_instance, self.attname):
objects.update(**{self.attname: False})
# If no true object exists that isnt saved model, save as True
elif not objects.exclude(id=model_instance.id)\
.filter(**{self.attname: True}):
return True
return getattr(model_instance, self.attname)
# To use with South
from south.modelsinspector import add_introspection_rules
add_introspection_rules([], ["^project\.apps\.fields\.UniqueBooleanField"])
models.py
from django.db import models
from project.apps.fields import UniqueBooleanField
class UniqueBooleanModel(models.Model):
unique_boolean = UniqueBooleanField()
def __unicode__(self):
return str(self.unique_boolean)
Trying to make ends meet with the answers here, I find that some of them address the same issue successfully and each one is suitable in different situations:
I would choose:
#semente: Respects the constraint at the database, model and admin form levels while it overrides Django ORM the least possible. Moreover it can be used inside a through table of a ManyToManyField in aunique_together situation.
class MyModel(models.Model):
is_the_chosen_one = models.BooleanField(null=True, default=None, unique=True)
def save(self, *args, **kwargs):
if self.is_the_chosen_one is False:
self.is_the_chosen_one = None
super(MyModel, self).save(*args, **kwargs)
Update: NullBooleanField will be deprecated by Django-4.0, for BooleanField(null=True).
#Ellis Percival: Hits the database only one extra time and accepts the current entry as the chosen one. Clean and elegant.
from django.db import transaction
class Character(models.Model):
name = models.CharField(max_length=255)
is_the_chosen_one = models.BooleanField()
def save(self, *args, **kwargs):
if not self.is_the_chosen_one:
# The use of return is explained in the comments
return super(Character, self).save(*args, **kwargs)
with transaction.atomic():
Character.objects.filter(
is_the_chosen_one=True).update(is_the_chosen_one=False)
# The use of return is explained in the comments
return super(Character, self).save(*args, **kwargs)
Other solutions not suitable for my case but viable:
#nemocorp is overriding the clean method to perform a validation. However, it does not report back which model is "the one" and this is not user friendly. Despite that, it is a very nice approach especially if someone does not intend to be as aggressive as #Flyte.
#saul.shanabrook and #Thierry J. would create a custom field which would either change any other "is_the_one" entry to False or raise a ValidationError. I am just reluctant to impement new features to my Django installation unless it is absoletuly necessary.
#daigorocub: Uses Django signals. I find it a unique approach and gives a hint of how to use Django Signals. However I am not sure whether this is a -strictly speaking- "proper" use of signals since I cannot consider this procedure as part of a "decoupled application".
The following solution is a little bit ugly but might work:
class MyModel(models.Model):
is_the_chosen_one = models.NullBooleanField(default=None, unique=True)
def save(self, *args, **kwargs):
if self.is_the_chosen_one is False:
self.is_the_chosen_one = None
super(MyModel, self).save(*args, **kwargs)
If you set is_the_chosen_one to False or None it will be always NULL. You can have NULL as much as you want, but you can only have one True.
class Character(models.Model):
name = models.CharField(max_length=255)
is_the_chosen_one = models.BooleanField()
def save(self, *args, **kwargs):
if self.is_the_chosen_one:
qs = Character.objects.filter(is_the_chosen_one=True)
if self.pk:
qs = qs.exclude(pk=self.pk)
if qs.count() != 0:
# choose ONE of the next two lines
self.is_the_chosen_one = False # keep the existing "chosen one"
#qs.update(is_the_chosen_one=False) # make this obj "the chosen one"
super(Character, self).save(*args, **kwargs)
class CharacterForm(forms.ModelForm):
class Meta:
model = Character
# if you want to use the new obj as the chosen one and remove others, then
# be sure to use the second line in the model save() above and DO NOT USE
# the following clean method
def clean_is_the_chosen_one(self):
chosen = self.cleaned_data.get('is_the_chosen_one')
if chosen:
qs = Character.objects.filter(is_the_chosen_one=True)
if self.instance.pk:
qs = qs.exclude(pk=self.instance.pk)
if qs.count() != 0:
raise forms.ValidationError("A Chosen One already exists! You will pay for your insolence!")
return chosen
You can use the above form for admin as well, just use
class CharacterAdmin(admin.ModelAdmin):
form = CharacterForm
admin.site.register(Character, CharacterAdmin)
And that's all.
def save(self, *args, **kwargs):
if self.default_dp:
DownloadPageOrder.objects.all().update(**{'default_dp': False})
super(DownloadPageOrder, self).save(*args, **kwargs)
class Character(models.Model):
name = models.CharField(max_length=255)
is_the_chosen_one = models.BooleanField()
def clean(self):
from django.core.exceptions import ValidationError
c = Character.objects.filter(is_the_chosen_one__exact=True)
if c and self.is_the_chosen:
raise ValidationError("The chosen one is already here! Too late")
Doing this made the validation available in the basic admin form
Using a similar approach as Saul, but slightly different purpose:
class TrueUniqueBooleanField(BooleanField):
def __init__(self, unique_for=None, *args, **kwargs):
self.unique_for = unique_for
super(BooleanField, self).__init__(*args, **kwargs)
def pre_save(self, model_instance, add):
value = super(TrueUniqueBooleanField, self).pre_save(model_instance, add)
objects = model_instance.__class__.objects
if self.unique_for:
objects = objects.filter(**{self.unique_for: getattr(model_instance, self.unique_for)})
if value and objects.exclude(id=model_instance.id).filter(**{self.attname: True}):
msg = 'Only one instance of {} can have its field {} set to True'.format(model_instance.__class__, self.attname)
if self.unique_for:
msg += ' for each different {}'.format(self.unique_for)
raise ValidationError(msg)
return value
This implementation will raise a ValidationError when attempting to save another record with a value of True.
Also, I have added the unique_for argument which can be set to any other field in the model, to check true-uniqueness only for records with the same value, such as:
class Phone(models.Model):
user = models.ForeignKey(User)
main = TrueUniqueBooleanField(unique_for='user', default=False)
Do I get points for answering my question?
problem was it was finding itself in the loop, fixed by:
# is this the testimonial image, if so, unselect other images
if self.testimonial_image is True:
others = Photograph.objects.filter(project=self.project).filter(testimonial_image=True)
pdb.set_trace()
for o in others:
if o != self: ### important line
o.testimonial_image = False
o.save()
I tried some of these solutions, and ended up with another one, just for the sake of code shortness (don't have to override forms or save method).
For this to work, the field can't be unique in it's definition but the signal makes sure that happens.
# making default_number True unique
#receiver(post_save, sender=Character)
def unique_is_the_chosen_one(sender, instance, **kwargs):
if instance.is_the_chosen_one:
Character.objects.all().exclude(pk=instance.pk).update(is_the_chosen_one=False)
2020 update to make things less complicated for beginners:
class Character(models.Model):
name = models.CharField(max_length=255)
is_the_chosen_one = models.BooleanField(blank=False, null=False, default=False)
def save(self):
if self.is_the_chosen_one == True:
items = Character.objects.filter(is_the_chosen_one = True)
for x in items:
x.is_the_chosen_one = False
x.save()
super().save()
Of course, if you want the unique boolean to be False, you would just swap every instance of True with False and vice versa.
When implementing a solution which overwrites model.save()*, I ran into the issue of Django Admin raising an error before hitting model.save(). The cause seems to be Admin calling model.clean() (or perhaps model.full_clean(), I didn't investigate too carefully) before calling model.save(). model.clean() in turn calls model.validate_unique() which raises a ValidationError before my custom save method can take care of the unique violation. To solve this I overwrote model.validate_unique() as follows:
def validate_unique(self, exclude=None):
try:
super().validate_unique(exclude=exclude)
except ValidationError as e:
validation_errors = e.error_dict
try:
list_validation_errors = validation_errors["is_the_chosen_one"]
for validation_error in list_validation_errors:
if validation_error.code == "unique":
list_validation_errors.remove(validation_error)
if not list_validation_errors:
validation_errors.pop(key)
except KeyError:
continue
if e.error_dict:
raise e
* the same would be true for a signal solution using pre_save, as pre_save is also not sent before .validate_unique is called