Django ModelChoiceField: filtering query set and setting default value as an object

Question

I have a Django Form class defined likes this in Models:

class AccountDetailsForm(forms.Form):
    ...
    adminuser = forms.ModelChoiceField(queryset=User.objects.all())

This works OK, but it has some limitations I can't seem to work around:

(1) I would like to use a filter on the queryset, based on a variable accountid passed to the form, like this:

User.objects.filter(account=accountid)

This can't work in the model because accountid can't be passed as a variable, of course.

It follows that the queryset must somehow be defined in the Views, but as far as I can see it's a required field in the Form class.

(2) I would like to make the default choice of AccountDetailsForm an object in the database, which I can select in the Views like this:

User.objects.filter(account=accountid).filter(primary_user=1)

I've tried specifying the adminuser as a default value in the form, (which works with other standard form fields, like CharField):

adminuser = User.objects.filter(account=accountid).filter(primary_user=1)

...

form = AccountDetailsForm({'adminuser': adminuser})
return render_to_response('accounts/edit/accountdetails.html', 
{'form': form, 'account':account})

But no luck.

Should I be using something other than ModelChoiceField given the flexibility I need here?

Thanks.

score 114 · Accepted Answer · answered Mar 16 '11 at 18:09

Override the init method and accept a new keyword argument

class AccountDetailsForm(forms.Form):
    ...
    adminuser = forms.ModelChoiceField(queryset=User.objects.all())
    def __init__(self, *args, **kwargs):
        accountid = kwargs.pop('accountid', None)
        super(AccountDetailsForm, self).__init__(*args, **kwargs)

        if accountid:
            self.fields['adminuser'].queryset = User.objects.filter(account=accountid)

form = AccountDetailsForm(accountid=3)

You can always just set the choices manually in the view as well.

form = AccountDetailsForm()
form.fields['adminuser'].queryset = User.objects.filter(account=accountid)

Be warned: you are not setting default values by passing in a dictionary to a form like in your example.

You are actually creating a Bound Form, potentially triggering validation and all that jazz.

To set defaults, use the initials argument.

form = AccountDetailsForm(initial={'adminuser':'3'})

Hi, thanks for your reply. Setting the queryset in the view worked well. The part I couldn't work out is setting the bound form value (rather than the default) of ModelChoiceField as _User.objects.filter(account=accountid).filter(primary_user=1)_. Thanks. — eli, Mar 16 '11 at 18:52

score 6 · Answer 2 · edited Sep 28 '12 at 19:30

6

You can override the field in the view

yourForm = AccountDetailsForm()

yourForm.fields['accomodation'] = forms.ModelChoiceField(User.objects.filter(account=accountid).filter(primary_user=1))

edited Sep 28 '12 at 19:30

andrewsi

10,807
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answered Sep 28 '12 at 16:41

Willians Vivanco

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1
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score 1 · Answer 3 · answered Aug 13 '20 at 20:50

Something that hasn't been mentioned here yet is the Form.clean() method. This method is specifically for custom validation.

For your example, you could do something like this:

class AccountDetailsForm(forms.Form):
    adminuser = forms.ModelChoiceField(queryset=User.objects.all())
    account_id = forms.IntegerField()  # or ModelChoiceField if that applies

    def clean(self):
        account_id = self.cleaned_data['account_id']
        self.cleaned_data['adminuser'] = User.objects.filter(account_id=account_id)

    return self.cleaned_data

The clean() method gets called after the default clean methods, so you can use self.cleaned_data (same as form.cleaned_data in the view) and return it however you'd like.

Even better, you can name the method according to the field you'd like to clean (def clean_adminuser) and make easier to read.

def clean_adminuser(self):
    account_id = self.cleaned_data['account_id']
    return User.objects.filter(account_id=account_id)

Also in this method you can call Form.add_error() if there are any issues you want to handle.

score 0 · Answer 4 · answered Jun 28 '18 at 08:51

0

In Django 2.0 you can pass object (User in your case) from the view to the form like this (you have to retrieve obj from the DB first):

form = AccountDetailsForm(initial={'adminuser': adminuser})

It will give you a default selected object (answers your 2) question)

answered Jun 28 '18 at 08:51

techkuz

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@JonProgrammer in the form? – techkuz Jul 25 '18 at 07:05
My current solution is that one here, but I feel it's not the most effective way: https://stackoverflow.com/questions/51512606/django-forms-queryset – Jul 25 '18 at 07:21

Django ModelChoiceField: filtering query set and setting default value as an object

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