I have a choiceField in order to create a select field with some options. Something like this:
forms.py
class NewForm(forms.Form):
title = forms.CharField(max_length=69)
parent = forms.ChoiceField(choices = CHOICE)
But I want to be able to create the options without having a predefined tuple (which is required by ChoiceField). Basically, I need to have access to request.user to fill some options tags according to each user, but I don't know if there is any way to use request in classes of forms.Form.
An alternative would be to prepopulate the instance of NewForm via:
views.py
form = NewForm(initial={'choices': my_actual_choices})
but I have to add a dummy CHOICE to create NewForm and my_actual_choices doesn't seem to work anyway.
I think a third way to solve this is to create a subclass of ChoiceField and redefined save() but I'm not sure how to go about doing this.
You can populate them dynamically by overriding the init, basically the code will look like:
class NewForm(forms.Form):
def __init__(self, choices, *args, **kwargs):
super(NewForm, self).__init__(*args, **kwargs)
self.fields["choices"] = forms.ChoiceField(choices=choices)
NewForm(my_actual_choices) or NewForm(my_actual_choices, request.POST, request.FILES) etc.
Related
I have an order model with a followed_by field:
class order(models.Model):
followed_by = models.ForeignKey(User, limit_choices_to={'groups__name': "Managers"})
I have several such models and forms for those models. By default the form displays a modelchoicefield listing users that are mangers. This is fine. But the display isn't nice: it gives the username, and I want first+last name. This would work nicely: Change Django ModelChoiceField to show users' full names rather than usernames
except that now in everyform I must declare the queryset to limit users to managers. Can I use the above method so that the custom modelchoicefield defaults to my filtered queryset. so then from a form I can just say:
followed_by = ManagerUserModelChoiceField()
Can you define the queryset on your ModelChoiceField child class?
class UserModelChoiceField(ModelChoiceField):
# Query that returns set of valid choices
queryset = User.objects.filter(group__name='Managers')
def label_from_instance(self, obj):
return obj.get_full_name()
Try passing in the queryset as an argument to the ManagerUserModelChoiceField class.
followed_by = ModelChoiceField(queryset = User.objects.filter(groups__name="Managers")
After my comment to #Enrico this thought occurred to me: I overwrote the "init" class on my custom field like so:
class UserModelChoiceField(forms.ModelChoiceField):
def __init__(self, *args, **kwargs):
super(UserModelChoiceField, self).__init__(queryset=User.objects.filter(groups__name="Managers"), *args, **kwargs)
I've seen stuff like this done in python before but I'm new to python so I'm not sure if this is a bad thing to do or if I should make this better somehow? I'd appreciate some feedback. That being said, it seems to be working correctly.
I followed the guide at https://docs.djangoproject.com/en/dev/ref/contrib/comments/custom/ to set up a comment form on News entries for my current django app. Now, I need to have a comment form with different fields for another type of Object in another part of the site.
How should this be accomplised considering I've overridden the contact form already?
That's a good question; django does seem pretty insistent that you use the same comment form everywhere. You can probably write a single form that shows different fields based on the object it's instantiated with. Try writing an init method along the lines of this:
class CustomCommentForm(CommentForm):
custom_field = forms.CharField(max_length=100)
def __init__(self, *args, **kwargs):
super(CustomCommentForm, self).__init__(*args, **kwargs)
# check what's in kwargs['initial'], and insert fields if needed like this:
if ...:
self.fields['optional_field'] = forms.CharField(max_length=100)
Suppose I want to create and update a model. What fields are displayed and the type of validation depends on the action (create or update). But they still share a lot of the same validation and functality. Is there a clean way to have a ModelForm handle this (besides just if instance exists everywhere) or should I just create two different model forms?
Two possibilities spring to mind. You could set an attribute in the form's __init__ method, either based on a parameter you explicitly pass in, or based on whether self.instance exists and has a non-None pk:
class MyModelForm(forms.ModelForm):
def __init__(self, *args, **kwargs):
# either:
self.edit = kwargs.pop('edit', False)
# or:
self.edit = hasattr(self, instance) and self.instance.pk is not None
super(MyModelForm, self).__init__(*args, **kwargs)
# now modify self.fields dependent on the value of self.edit
The other option is to subclass your modelform - keep the joint functionality in the base class, then the specific create or update functionality in the subclasses.
How do I allow fields to be populated by the user at the time of object creation ("add" page) and then made read-only when accessed at "change" page?
The simplest solution I found was to override the get_readonly_fields function of ModelAdmin:
class TestAdmin(admin.ModelAdmin):
def get_readonly_fields(self, request, obj=None):
'''
Override to make certain fields readonly if this is a change request
'''
if obj is not None:
return self.readonly_fields + ('title',)
return self.readonly_fields
admin.site.register(TestModel, TestAdmin)
Object will be none for the add page, and an instance of your model for the change page.
Edit: Please note this was tested on Django==1.2
There's two thing to address in your question.
1. Read-only form fields
Doesn't exist as is in Django, but you can implement it yourself, and this blog post can help.
2. Different form for add/change
I guess you're looking for a solution in the admin site context (otherwise, just use 2 different forms in your views).
You could eventually override add_view or change_view in your ModelAdmin and use a different form in one of the view, but I'm afraid you will end up with an awful load of duplicated code.
Another solution I can think of, is a form that will modify its fields upon instantiation, when passed an instance parameter (ie: an edit case). Assuming you have a ReadOnlyField class, that would give you something like:
class MyModelAdminForm(forms.ModelForm):
class Meta:
model = Stuff
def __init__(self, *args, **kwargs):
super(MyModelAdminForm, self).__init__(*args, **kwargs)
if kwargs.get('instance') is not None:
self.fields['title'] = ReadOnlyField()
In here, the field title in the model Stuff will be read-only on the change page of the admin site, but editable on the creation form.
Hope that helps.
You can edit that model's save method to handle such a requirement. For example, you can check if the field already contains some value, if it does, ignore the new value.
One option is to override or replace the change_form template for that specific model.
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