I want to get rid of the "-------------" choice Django adds in a select input representing a Foreign Key on a ModelForm
It's been answered that you can use the empty_label=none option, but I have a ModelForm, not a regular form and overriding the field is not allowed.
I know that I can override the __init__() method of the ModelForm in order to modify a ModelChoiceField's queryset using
self.fields['my_foreign_key'].queryset = ....
But this would be really ugly, as this happens over +10 foreign_keys on the "Main" model, and there's more than a Modelform based on this model
The whole context :
each one of these foreign_key points to the same kind of models : they are particular lists of choices, many models to ease their modification via the admin.
all these models are related to the Main model via a "to_field=code" relation, based on a Charfield which contains a three-letter code (hey, not my fault, I had to use a legacy MS Access DB), this CharField has the blank=True, unique=True options, so I could, for each list, create a "---No information yet---" record which has, you bet, a blank value instead of a three letter code...
The situation is now : I get a select input field with two "blank value" choices : the django one and mine, one after the other.
I just miss a 'empty_label=none` option here too...
If you want to remove the blank choice for all ModelChoiceField you could do something like..
class Form(forms.ModelForm):
class Meta:
model = MyModel
def __init__(self, *args, **kwargs):
super(Form, self).__init__(*args, **kwargs)
modelchoicefields = [field for field_name, field in self.fields.iteritems() if
isinstance(field, forms.ModelChoiceField)]
for field in modelchoicefield:
field.empty_label = None
But that would replace all ModelChoiceFields, so maybe something more fine grained like:
for fieldname in ('field1','field2','field3','field4','field5','field6'):
self.fields[fieldname].empty_label = None
Certainly easier than the __init__ overwrite you mentioned!
Update from Moritz
You can use 2017+ use:
forms.ModelChoiceField(... empty_label=None
Related
I have a Django model with a Foreign key to a table that contains about 50,000 records. I am using the Django forms.ModelForm to create a form. The problem is I only need a small subset of the records from the table the Foreign key points to.
I am able to create that subset of choices in the init method. How can I prevent ModelForm from creating that initial set of choices?
I tried using the widgets parameter in the Meta method. But Django debug toolbar indicates the database is still being hit.
Thanks
The autogenerated ModelChoiceField will have its queryset initialized to the default. The widget is not where you are supposed to customize the queryset property.
Define the ModelChoiceField manually, initialize its queryset to be empty. Remember to name the ModelChoiceField the same as the one that would have been automatically generated, and remember to mention that field in the fields tuple. Now you can set the queryset from the constructor and avoid the database being hit twice.
If you are lucky (and you probably are, please test though), the queryset has not been evaluated during construction, and in that case, defining the ModelChoiceField manually is not required.
class YourModelForm(ModelForm):
your_fk_field_name = forms.ModelChoiceField(queryset=YourModel.objects.none())
class Meta:
model = YourModel
fields = ('your_fk_field_name', .......)
def __init__(self, *args, **kwargs):
super(YourModelForm, self).__init__(*args, **kwargs)
self.fields['your_fk_field_name'].queryset = ....
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 currently have a model set up like so:
I have a Test class with a foreign key to a custom UserProfile class. This property is called student. So each UserProfile may have taken more than one Test. Then in turn, each UserProfile is tied to a User by the typical onetoone relation. Another level of complexity is added because I have declared two user groups tutors and students. And the UserProfile class has a ManyToMany relation on to itself labeled "tutors". The logic is that each student may have many tutors teaching him. Now what I would like to do is add filters on the right-hand side of the Test admin page that lets you filter by the student and filter by tutor as well. setting list_filter = ('student',) simply lists all available UserProfiles. But this would include the UserProfiles which are tied to tutors as well. Obviously I would like to filter this list down to only students, because clearly filtering by any of these tutors would result in an empty queryset. I would then like to do a similar thing with filtering by tutor, where in this case the shorthand would be list_filter = ('student__tutors'), but I'd want this UserProfile set to be filtered down to only include those where user_groups_name='tutors'. What is the best way to do this?
For clarity, my object model looks like this:
class UserProfile(models.Model):
user = models.OneToOneField(User, unique=True,related_name='profile')
tutors = models.ManyToManyField("self",related_name="students")
class Test(models.Model):
student = models.ForeignKey(UserProfile,related_name='tests')
I tried subclassing django.contrib.admin.SimpleListFilter with the following:
class StudentListFilter(SimpleListFilter):
title = 'student'
parameter_name = 'student__id__exact'
def lookups(self, request, model_admin):
qs = model_admin.queryset(request)
return User.objects.filter(profile__id__in=qs.values_list('student__id')).extra(select={'full_name':'first_name||" "||last_name'}).values_list('profile__id','full_name')
def queryset(self, request, queryset):
if self.value() is not None:
return queryset.filter(student__id__exact=self.value())
else:
return queryset
Which seems to work for the first list_filter, but the trouble is for some reason there's a bug now where the selected option does not get highlighted in the custom filter. Only 'All' highlights but not the custom options. Here is an example of it that another user posted:
http://imgur.com/lyrYk
I am currently using the development version of django 1.4, so I'm not sure if this issue is tied to that or not.
Interesting problem.
I think you need to convert your lookups to a string.
return [(str(x), y) for x, y in your_valuesqueryset]
Line 98 on django.admin.filters defines the selected filter as:
'selected': self.value() == lookup
Where the lookup is populated directly from the results of the lookups method.
The auto type coercion in your filter() call is making the filter succeed but '2' != 2
I have a deal model that contains two date field. First one is start_date and the other one is end_date. My aim is when I save a deal I want to update a readonly field which shows the substraction of these two date_field.
I try to write a widget however I can only get one of the fields. Here is my widget:
class DueToWidget(AdminDateWidget):
def render(self,name,value,attrs=None):
from datetime import timedelta
output = []
output.append(super(AdminDateWidget, self).render(name,value,attrs))
if value:
due_to = value + timedelta(days=1)
output.append(u'<p>Diff : %s</p>' % due_to)
return mark_safe(u''.join(output))
I'm adding one day to the selected date, how can I get the other field's value ? Or is there any other way to do this ?
If you don't mind having to refresh to see the diff (that is, you only see it after you save the model), then an easier approach is to add a readonly field in the admin, that points to a function, like this:
class MyModelAdmin(ModelAdmin):
readonly_fields = ('dates_difference',)
#add your other fields, or put it in a fieldset
fields = ('dates_difference',)
def dates_difference(self, model_instance):
return model_instance.end_date - model_instance.start_date
Since your goal is just to display extra information in the model's admin this is the place to put the code, not in a field's widget or the model's class.
As the readonly_fields documentation specifies, its behavior is nearly identical as the list_display, that is you can point it to attributes on both the model and the model's admin, and also to callables and methods.
Override save() in the model to save computed data.
def save( self, *args, **kw ):
self.diff = self.end_date - self.start_date
return super( YourModelClass, self ).save( *args, **kw )
Learn more by reading the Django documentation on the subject.
Given a model with ForeignKeyField (FKF) or ManyToManyField (MTMF) fields with a foreignkey to 'self' how can I prevent self (recursive) selection within the Django Admin (admin).
In short, it should be possible to prevent self (recursive) selection of a model instance in the admin. This applies when editing existing instances of a model, not creating new instances.
For example, take the following model for an article in a news app;
class Article(models.Model):
title = models.CharField(max_length=100)
slug = models.SlugField()
related_articles = models.ManyToManyField('self')
If there are 3 Article instances (title: a1-3), when editing an existing Article instance via the admin the related_articles field is represented by default by a html (multiple)select box which provides a list of ALL articles (Article.objects.all()). The user should only see and be able to select Article instances other than itself, e.g. When editing Article a1, related_articles available to select = a2, a3.
I can currently see 3 potential to ways to do this, in order of decreasing preference;
Provide a way to set the queryset providing available choices in the admin form field for the related_articles (via an exclude query filter, e.g. Article.objects.filter(~Q(id__iexact=self.id)) to exclude the current instance being edited from the list of related_articles a user can see and select from. Creation/setting of the queryset to use could occur within the constructor (__init__) of a custom Article ModelForm, or, via some kind of dynamic limit_choices_to Model option. This would require a way to grab the instance being edited to use for filtering.
Override the save_model function of the Article Model or ModelAdmin class to check for and remove itself from the related_articles before saving the instance. This still means that admin users can see and select all articles including the instance being edited (for existing articles).
Filter out self references when required for use outside the admin, e.g. templates.
The ideal solution (1) is currently possible to do via custom model forms outside of the admin as it's possible to pass in a filtered queryset variable for the instance being edited to the model form constructor. Question is, can you get at the Article instance, i.e. 'self' being edited the admin before the form is created to do the same thing.
It could be I am going about this the wrong way, but if your allowed to define a FKF / MTMF to the same model then there should be a way to have the admin - do the right thing - and prevent a user from selecting itself by excluding it in the list of available choices.
Note: Solution 2 and 3 are possible to do now and are provided to try and avoid getting these as answers, ideally i'd like to get an answer to solution 1.
Carl is correct, here's a cut and paste code sample that would go in admin.py
I find navigating the Django relationships can be tricky if you don't have a solid grasp, and a living example can be worth 1000 time more than a "go read this" (not that you don't need to understand what is happening).
class MyForm(forms.ModelForm):
class Meta:
model = MyModel
def __init__(self, *args, **kwargs):
super(MyForm, self).__init__(*args, **kwargs)
self.fields['myManyToManyField'].queryset = MyModel.objects.exclude(
id__exact=self.instance.id)
You can use a custom ModelForm in the admin (by setting the "form" attribute of your ModelAdmin subclass). So you do it the same way in the admin as you would anywhere else.
You can also override the get_form method of the ModelAdmin like so:
def get_form(self, request, obj=None, **kwargs):
"""
Modify the fields in the form that are self-referential by
removing self instance from queryset
"""
form = super().get_form(request, obj=None, **kwargs)
# obj won't exist yet for create page
if obj:
# Finds fieldnames of related fields whose model is self
rmself_fields = [f.name for f in self.model._meta.get_fields() if (
f.concrete and f.is_relation and f.related_model is self.model)]
for fieldname in rmself_fields:
form.base_fields[fieldname]._queryset =
form.base_fields[fieldname]._queryset.exclude(id=obj.id)
return form
Note that this is a on-size-fits-all solution that automatically finds self-referencing model fields and removes self from all of them :-)
I like the solution of checking at save() time:
def save(self, *args, **kwargs):
# call full_clean() that in turn will call clean()
self.full_clean()
return super().save(*args, **kwargs)
def clean(self):
obj = self
parents = set()
while obj is not None:
if obj in parents:
raise ValidationError('Loop error', code='infinite_loop')
parents.add(obj)
obj = obj.parent