Is there an obvious way to convert a ModelForm into a regular Form without the instance setting logic?
I have an Update/Create ModelForm View I'd like to convert into a SearchView by using input from the exact same list of fields to query the model but it causes problems with required fields and types since the ModelForm attaches data to self.instance immediately.
I've ended up hacking into the metaclass to get what I want but I feel like I could easily be missing some solution right before my eyes overriding some function. I don't really enjoy pulling core django code...
Other forms of hackery would be preferable to copy and pasting the entire metaclass.
class ModelFormMetaclass(type):
def __new__(cls, name, bases, attrs):
formfield_callback = attrs.pop('formfield_callback', None)
try:
parents = [b for b in bases if issubclass(b, ModelToForm)] #<-- here
# ... rest of class
class ModelToForm(BaseForm):
__metaclass__ = ModelFormMetaclass
Update:
It appears ModelForm._post_clean() is responsible for instance construction / related field validation.
Currently I'm disabling _post_clean() and seeing where that takes me.
Related
Thanks in advance for reading this. I can't wrap my head around it and it's getting quite frustrating by now.
We have the following registration form:
class RegistrationForm(forms.ModelForm):
class Meta:
model = Register
fields = ('name', 'company_name')
def clean(self):
if is not self.cleaned_data.get('card').is_available():
raise forms.ValidationError(_('Error'))
The Register model includes a card linked to a Card model. This includes is_available() which functionally works.
Our flow is:
The end user selects the card which lists all registrations for it.
They click the 'Add registration'-button which brings them to cards/{PK}/add.
The Add registration-button is a generic.View. In post(self, request, pk) I have the following code:
form = RegistrationForm(request.POST)
But how do I pass it the contents of Card.objects.get(pk=pk) to it?
I tried:
data = request.POST.copy()
data['card'] = pk
form = RegistrationForm(data)
But I think because card is not included in fields it gets lost somewhere, which makes sense from a sanitize-all-input-point of view, but I would very much like to add the card dynamically, in this case.
Any ideas?
So, just use CreateView and study how it does things using the linked site.
There is no need to use generic.View as it's the basic of basics. You only want to implement all this logic using generic.View to get more familiar with the way things work or if you need some very special form handling.
The short version would be:
from django.views import generic
from myapp.forms import RegistrationForm
class CardCreateView(generic.CreateView):
form_class = RegistrationForm
ModelForm has a save method. The correct way to solve this is to use it with commit=False, that will return an object that hasn’t yet been saved to the database. Then you can alter that object before finally saving it.
This is explained here in the docs
So this is what your code should look like:
form = RegistrationForm(request.POST)
form.save(commit=False)
form.card = Card.objects.get(pk=pk)
form.save_m2m()
save_m2m should be used if your model has many-to-many relationships with other models. In my case, it was a OneToOne, so I used save() instead.
If you use a CreateView instead of the generic View, the snippet above should go into your overridden form_valid method
In Django's admin, you can add instance method calls to an edit page via the readonly option.
Can I do something similar with a ModelForm, and display the results of an instance method call? Preferably making it part of the forms visible_fields list.
My templates are quite generic so they are looping through the forms visible fields list and I would prefer not to alter these.
Oke, my solution will be quite hacky, but you could maybe do something like this:
class YourModelForm(forms.ModelForm):
class Meta:
model = YourModel
fields = []
def __init__(self, *args, *kwargs):
super(YourModelForm, self).__init__(*args, **kwargs)
# You can also user insert, to add on a certain position
self.visible_fields.append(self.instance.method())
Now a problem could be that you append a value, because I don't know how you render your fields. But you could fix this by append a Field-like object, which returns escaped (and saved) html on the necessary methods you call.
Other hacky option, add an additional field, set with an widget its attributes to disabled=disabled, and since a disabled input value isn't submitted with the form, set it required=False.
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()