My issue is that my app is not allowing me to update a OneToOneField field. Here's my explanation of what I'm trying to do.
I am building an inventory app that keeps track of instruments that have been loaned to students. There will always be a one-to-one database relationship between students and instruments. So an individual student can't ever have more than one instrument and vice versa.
I therefore created an Intrument model that looks like this:
class Instrument(models.Model):
instrument_type = models.CharField(max_length=100)
needs_repairs = models.BooleanField()
inventory_id = models.CharField(max_length=100)
student = models.OneToOneField(Student, null=True, blank=True, default = None)
I have created a form that allows me to update existing students, and I'm trying to use as much built-in stuff as possible so that I don't need to re-write validation code or HTML. So I'm using a ModelForm object and validating my input using the is_valid() method.
Here's an example of a POST request to update an instrument:
csrfmiddlewaretoken=xyUBhVuQZus6XmeV2DhCmpJHwIXVmdHm&instrument_type=Viola&inventory_id=abcde&student=3
Please note that the only field with a uniqueness constraint is student.
So finally, here's the problem: when I call the is_valid() method it always fails with an error saying that the student has already been assigned to an instrument.
My first thought was to use the framework to add some pre-validation code that didn't error if the student pkey didn't change. This certainly seems easy enough, but it seems to be a bit hacky to me. I assumed that one-to-one relationships would "just work" like all of the other Model fields and that no special validation would be required.
But then I read the API docs for the OneToOneField class and it doesn't seem to address one-to-one database relationships - it seems to address one-to-one OO relationships. So I may be using the wrong Model field type all together. And since this is such a simple app, I'm not performing a ton of OO modeling - I'm just worried about proper data modeling :-)
So am I using the wrong field, or is the "proper" way to fix this to add pre-validation code to my Student model?
Updates From Comments
Here's the closest thing that I have to a stack trace:
>>> data = {'instrument_type': 'Viola', 'inventory_id': 'abcde', 'student': 3, 'repairer': 1}
>>> form = InstrumentForm(data)
>>> form.is_bound
True
>>> form.is_valid()
False
>>> form.errors
{'student': [u'Instrument with this Student already exists.']}
I use a single view method to display Instrument detail and update a single Instrument. Here's that:
def instrument_detail(request, instrument_id):
try:
instrument = Instrument.objects.get(pk=instrument_id)
except Instrument.DoesNotExist:
raise Http404
# Default if not a POST
form = InstrumentForm(instance=instrument)
if request.method == 'POST':
form = InstrumentForm(request.POST)
if form.is_valid():
form.save()
return HttpResponseRedirect(reverse('instruments.views.instruments_index'))
# otherwise...
t = loader.get_template('instruments/details.html')
c = RequestContext(request, {
'instrument': instrument,
'form': form,
})
return HttpResponse(t.render(c))
You're not passing the instance when instantiating the form on POST.
if request.method == 'POST':
form = InstrumentForm(request.POST, instance=instrument)
Related
I have a form with some fields. I want to display all fields in form except two. However one field data needs to be displayed.
I am able to get the form but not able to retrieve the data from DB to display.
Model.py
class Company(models.Model):
STATUS_CHOICES=(
('service','service'),
('product','product'),
)
user=models.OneToOneField(settings.AUTH_USER_MODEL)
company_name=models.CharField(max_length=250)
company_address=models.CharField(max_length=250)
Company_telephone=models.CharField(max_length=250,blank=True)
company_email=models.CharField(max_length=250,blank=True)
company_website=models.CharField(max_length=250,blank=True)
VAT=models.CharField(max_length=250,blank=True)
Service_Tax=models.CharField(max_length=250,blank=True)
company_PAN=models.CharField(max_length=250,blank=True)
company_bankdetails=models.CharField(max_length=250,blank=True)
invoice_type=models.CharField(max_length=250,choices=STATUS_CHOICES,default='service')
def __str__(self):
return 'self.user.company_name'
forms.py
class companyeditform(forms.ModelForm):
class Meta:
model=Company
exclude = ('user','company_name',)
views.py
#login_required
def companyadd(request):
if request.method == 'POST':
company_form=companyeditform(instance=request.user.company,data=request.POST)
if company_form.is_valid():
new_form=company_form.save(commit=False)
new_form.save()
return render(request,'account/dashboard.html',{'section':'addcompany'})
else:
company_form=companyeditform(instance=request.user.company)
company_details=Company.objects.get(user=request.user.company)
return render(request,'account/company.html',{'company_form':company_form})
When form is displayed everything works as planned. However not getting company_name.
Using this query to get company name.
company_details=Company.objects.get(user=request.user.company)
Django gives following error:
Cannot query "self.user.company_name": Must be "User" instance.
In this query company_details=Company.objects.get(user=request.user.company) you are trying to get the company of a particular user. But in the statement, you are comparing user=request.user.company, both are two different types (User is the authuser model and request.user.company is the Company model). You cannot do this in the query.
company_details=Company.objects.get(user=request.user) This statement will solve the issue. And also you can do
company_details=request.user.company because the association is OneToOne.
The reason you are getting that error, is because you are trying to fetch a Company by filtering it out the company that matches the current user, but you are passing in the actual company object:
company_details=Company.objects.get(user=request.user.company)
# ^^^^^^^
You can fix the line, by doing this:
company_details=Company.objects.get(user=request.user)
But you already have the correct object, in request.user.company, you don't need to fetch it again, simply:
company_details = request.user.company
print(company_details.company_name)
In fact, since you are using the render shortcut, you don't even need to do this step, as the request object will be available in your template, so all you need to do really is:
Company: {{ request.user.company.company_name }}
Finally, you should always redirect after a POST request (see this article on wikipedia for the details).
request.user might be a class like AnonymousUser. Do some extra processing to ensure that request.user is the type provided by django.contrib.auth.get_user_model().
I know that many questions exist about this same topic, but i am confused on one point.
My intent is to show two ModelChoiceFields on the form, but not directly tie them to the Game model.
I have the following:
forms.py
class AddGame(forms.ModelForm):
won_lag = forms.ChoiceField(choices=[('1','Home') , ('2', 'Away') ])
home_team = forms.ModelChoiceField(queryset=Player.objects.all())
away_team = forms.ModelChoiceField(queryset=Player.objects.all())
class Meta:
model = Game
fields = ('match', 'match_sequence')
Views.py
def game_add(request, match_id):
game = Game()
try:
match = Match.objects.get(id=match_id)
except Match.DoesNotExist:
# we have no object! do something
pass
game.match = match
# get form
form = AddGame(request.POST or None, instance=game)
form.fields['home_team'].queryset = Player.objects.filter(team=match.home_team )
# handle post-back (new or existing; on success nav to game list)
if request.method == 'POST':
if form.is_valid():
form.save()
# redirect to list of games for the specified match
return HttpResponseRedirect(reverse('nine.views.list_games'))
...
Where i am confused is when setting the queryset filter.
First i tried:
form.home_team.queryset = Player.objects.filter(team=match.home_team )
but i got this error
AttributeError at /nine/games/new/1
'AddGame' object has no attribute 'home_team'
...
so i changed it to the following: (after reading other posts)
form.fields['home_team'].queryset = Player.objects.filter(team=match.home_team )
and now it works fine.
So my question is, what is the difference between the two lines? Why did the second one work and not the first? I am sure it is a newbie (i am one) question, but i am baffled.
Any help would be appreciated.
Django Forms are metaclasses:
>>> type(AddGame)
<class 'django.forms.forms.DeclarativeFieldsMetaclass'>
They basically create a form instance according to the information given in its definition. This means, you won't get exactly what you see when you define the AddGame form. When you instantiate it, the metaclass will return the proper instance with the fields provided:
>>> type(AddGame())
<class 'your_app.forms.AddGame'>
So, with the instance, you can access the fields by simply doing form.field. In fact, it is a bit more complicated than that. There are two types of fields you can access. With form['field'] you'll be accessing a BoundField. Which is used for output and raw_input.
By doing form.fields['fields'] you'll be then accessing to a field that python can understand. This is because if the from already got any input, there's where validation and data conversion take places (in fact, those are the fields used for this, the general process of validation is a bit more complicated).
I hope this might clear a little the issue for you but as you may see, the whole form's API is really big and complicated. Is very simple for end-users but it has a lot of programming behind the curtains :)
Reading the links provides will help clear your doubts and will improve your knowledge about this very useful topic and Django in general.
Good luck!
UPDATE: By the way, if you want to learn more about Python's Metaclasses, this is a hell of an answer about the topic.
In you views.py, you have this line:
form = AddGame(request.POST or None, instance=game)
So form is a Form object of class AddGame (Side note: you should change the name to AddGameForm to avoid confusion).
Since home_team is a field in AddGame class, it's not an attribute in form object. That's why you can't access it via form.home_team.
However, Django Form API provides fields attribute to any form object, which is a dict contains all form fields. That's why you can access form.fields['home_team'].
And finally since home_team is a ModelChoiceField, it can contain a queryset attribute, that's why you can access form.fields['home_team'].queryset
I'm still trying to understand the correct way to validate a Django model object using a custom validator at the model level. I know that validation is usually done within a form or model form. However, I want to ensure the integrity of my data at the model level if I'm interacting with it via the ORM in the Python shell. Here's my current approach:
from django.db import models
from django.core import validators
from django.core exceptions import ValidationError
def validate_gender(value):
""" Custom validator """
if not value in ('m', 'f', 'M', 'F'):
raise ValidationError(u'%s is not a valid value for gender.' % value)
class Person(models.Model):
name = models.CharField(max_length=128)
age = models.IntegerField()
gender = models.CharField(maxlength=1, validators=[validate_gender])
def save(self, *args, **kwargs):
""" Override Person's save """
self.full_clean(exclude=None)
super(Person, self).save(*args, **kwargs)
Here are my questions:
Should I create a custom validation function, designate it as a validator, and then override the Person's save() function as I've done above? (By the way, I know I could validate my gender choices using the 'choices' field option but I created 'validate_gender' for the purpose of illustration).
If I really want to ensure the integrity of my data, should I not only write Django unit tests for testing at the model layer but also equivalent database-level unit tests using Python/Psycopg? I've noticed that Django unit tests, which raise ValidationErrors, only test the model's understanding of the database schema using a copy of the database. Even if I were to use South for migrations, any database-level constraints are limited to what Django can understand and translate into a Postgres constraint. If I need a custom constraint that Django can't replicate, I could potentially enter data into my database that violates that constraint if I'm interacting with the database directly via the psql terminal.
Thanks!
I had a similar misunderstanding of the ORM when I first started with Django.
No, don't put self.full_clean() inside of save. Either
A) use a ModelForm (which will cause all the same validation to occur - note: ModelForm.is_valid() won't call Model.full_clean explicitly, but will perform the exact same checks as Model.full_clean). Example:
class PersonForm(forms.ModelForm):
class Meta:
model = Person
def add_person(request):
if request.method == 'POST':
form = PersonForm(request.POST, request.FILES)
if form.is_valid(): # Performs your validation, including ``validate_gender``
person = form.save()
return redirect('some-other-view')
else:
form = PersonForm()
# ... return response with ``form`` in the context for rendering in a template
Also note, forms aren't for use only in views that render them in templates - they're great for any sort of use, including an API, etc. After running form.is_valid() and getting errors, you'll have form.errors which is a dictionary containing all the errors in the form, including a key called '__all__' which will contain non-field errors.
B) Simply use model_instance.full_clean() in your view (or other logical application layer), instead of using a form, but forms are a nice abstraction for this.
I don't really have a solution to, but I've never run into such a problem, even in large projects (the current project I work with my company on has 146 tables) and I don't suspect it'll be a concern in your case either.
In a Django app, I'm having a model Bet which contains a ManyToMany relation with the User model of Django:
class Bet(models.Model):
...
participants = models.ManyToManyField(User)
User should be able to start new bets using a form. Until now, bets have exactly two participants, one of which is the user who creates the bet himself. That means in the form for the new bet you have to chose exactly one participant. The bet creator is added as participant upon saving of the form data.
I'm using a ModelForm for my NewBetForm:
class NewBetForm(forms.ModelForm):
class Meta:
model = Bet
widgets = {
'participants': forms.Select()
}
def save(self, user):
... # save user as participant
Notice the redefined widget for the participants field which makes sure you can only choose one participant.
However, this gives me a validation error:
Enter a list of values.
I'm not really sure where this comes from. If I look at the POST data in the developer tools, it seems to be exactly the same as if I use the default widget and choose only one participant. However, it seems like the to_python() method of the ManyToManyField has its problems with this data. At least there is no User object created if I enable the Select widget.
I know I could work around this problem by excluding the participants field from the form and define it myself but it would be a lot nicer if the ModelForm's capacities could still be used (after all, it's only a widget change). Maybe I could manipulate the passed data in some way if I knew how.
Can anyone tell me what the problem is exactly and if there is a good way to solve it?
Thanks in advance!
Edit
As suggested in the comments: the (relevant) code of the view.
def new_bet(request):
if request.method == 'POST':
form = NewBetForm(request.POST)
if form.is_valid():
form.save(request.user)
... # success message and redirect
else:
form = NewBetForm()
return render(request, 'bets/new.html', {'form': form})
After digging in the Django code, I can answer my own question.
The problem is that Django's ModelForm maps ManyToManyFields in the model to ModelMultipleChoiceFields of the form. This kind of form field expects the widget object to return a sequence from its value_from_datadict() method. The default widget for ModelMultipleChoiceField (which is SelectMultiple) overrides value_from_datadict() to return a list from the user supplied data. But if I use the Select widget, the default value_from_datadict() method of the superclass is used, which simply returns a string. ModelMultipleChoiceField doesn't like that at all, hence the validation error.
To solutions I could think of:
Overriding the value_from_datadict() of Select either via inheritance or some class decorator.
Handling the m2m field manually by creating a new form field and adjusting the save() method of the ModelForm to save its data in the m2m relation.
The seconds solution seems to be less verbose, so that's what I will be going with.
I don't mean to revive a resolved question but I was working a solution like this and thought I would share my code to help others.
In j0ker's answer he lists two methods to get this to work. I used method 1. In which I borrowed the 'value_from_datadict' method from the SelectMultiple widget.
forms.py
from django.utils.datastructures import MultiValueDict, MergeDict
class M2MSelect(forms.Select):
def value_from_datadict(self, data, files, name):
if isinstance(data, (MultiValueDict, MergeDict)):
return data.getlist(name)
return data.get(name, None)
class WindowsSubnetForm(forms.ModelForm):
port_group = forms.ModelMultipleChoiceField(widget=M2MSelect, required=True, queryset=PortGroup.objects.all())
class Meta:
model = Subnet
The problem is that ManyToMany is the wrong data type for this relationship.
In a sense, the bet itself is the many-to-many relationship. It makes no sense to have the participants as a manytomanyfield. What you need is two ForeignKeys, both to User: one for the creator, one for the other user ('acceptor'?)
You can modify the submitted value before (during) validation in Form.clean_field_name. You could use this method to wrap the select's single value in a list.
class NewBetForm(forms.ModelForm):
class Meta:
model = Bet
widgets = {
'participants': forms.Select()
}
def save(self, user):
... # save user as participant
def clean_participants(self):
data = self.cleaned_data['participants']
return [data]
I'm actually just guessing what the value proivded by the select looks like, so this might need a bit of tweaking, but I think it will work.
Here are the docs.
Inspired by #Ryan Currah I found this to be working out of the box:
class M2MSelect(forms.SelectMultiple):
def render(self, name, value, attrs=None, choices=()):
rendered = super(M2MSelect, self).render(name, value=value, attrs=attrs, choices=choices)
return rendered.replace(u'multiple="multiple"', u'')
The first one of the many to many is displayed and when saved only the selected value is left.
I found an easyer way to do this inspired by #Ryan Currah:
You just have to override "allow_multiple_selected" attribut from SelectMultiple class
class M2MSelect(forms.SelectMultiple):
allow_multiple_selected = False
class NewBetForm(forms.ModelForm):
class Meta:
model = Bet
participants = forms.ModelMultipleChoiceField(widget=M2MSelect, required=True, queryset=User.objects.all())
I'm making a settings interface which works by scanning for a settings folder in the installed applications, scanning for settings files, and finally scanning for ModelForms.
I'm at the last step now. The forms are properly found and loaded, but I now need to provide the initial data. The initial data is to be pulled from the database, and, as you can imagine, it must be limited to the authenticated user (via request.user.id).
Keep in mind, this is all done dynamically. None of the names for anything, nor their structure is known in advanced (I really don't want to maintain a boring settings interface).
Here is an example settings form. I just pick the model and which fields the user can edit (this is the extent to which I want to maintain a settings interface).
class Set_Personal_Info(forms.ModelForm):
class Meta:
model = UserProfile
fields = ('nick_name', 'url')
I've looked at modelformset_factory which almost does what I want to do, but it only seems to work with results of two or more. (Here, obj is one of the settings forms)
Formset = modelformset_factory(obj.Meta.model, form=obj)
Formset(queryset=obj.Meta.model.objects.filter(id=request.user.id))
I can't filter the data, I have to get one, and only one result. Unfortunately I can't use get()
Formset = modelformset_factory(obj.Meta.model, form=obj)
Formset(queryset=obj.Meta.model.objects.get(id=request.user.id))
'User' object has no attribute 'ordered'
Providing the query result as initial data also doesn't work as it's not a list.
Formset = modelformset_factory(obj.Meta.model, form=obj)
Formset(initial=obj.Meta.model.objects.get(id=request.user.id))
'User' object does not support indexing
I have a feeling that the answer is right in front of me. How can I pull database from the database and shove it into the form as initial values?
I'm not really sure I understand what you're trying to do - if you're just interested in a single form, I don't know why you're getting involved in formsets at all.
To populate a modelform with initial data from the database, you just pass the instance argument:
my_form = Set_Personal_Info(instance=UserProfile.objects.get(id=request.user.id))
Don't forget to also pass the instance argument when you're instantiating the form on POST, so that Django updates the existing instance rather than creating a new one.
(Note you might want to think about giving better names to your objects. obj usually describes a model instance, rather than a form, for which form would be a better name. And form classes should follow PEP8, and probably include the word 'form' - so PersonalInfoForm would be a good name.)
Based on what I've understand ... if you want to generate a form with dynamic fields you can use this:
class MyModelForm(forms.ModelForm):
def __init__(self, dynamic_fields, *args, **kwargs):
super(MyModelForm, self).__init__(*args, **kwargs)
self.fields = fields_for_model(self._meta.model, dynamic_fields, self._meta.exclude, self._meta.widgets)
class Meta:
model = MyModel
Where dynamic_fields is a tuple.
More on dynamic forms:
http://www.rossp.org/blog/2008/dec/15/modelforms/
http://jacobian.org/writing/dynamic-form-generation/
http://dougalmatthews.com/articles/2009/dec/16/nicer-dynamic-forms-django/
Also Daniel's approach is valid and clean ... Based on your different ids/types etc you can you use different Form objects
forms.py
class MyModelFormA(forms.ModelForm):
class Meta:
model = MyModel
fields = ('field_a','field_b','field_c')
class MyModelFormB(forms.ModelForm):
class Meta:
model = MyModel
fields = ('field_d','field_e','field_f')
views.py
if request.method == 'POST':
if id == 1:
form = MyModelFormA(data=request.POST)
elif id == 2:
form = MyModelFormB(data=request.POST)
else:
form = MyModelFormN(data=request.POST)
if form.is_valid():
form.save() else:
if id == 1:
form = MyModelFormA()
elif id == 2:
form = MyModelFormB()
else:
form = MyModelFormN()