Keeping field values on Form fields after request.GET - but also passing other kwargs

Question

I have this form:

class TaskSelectForm(forms.Form):
    def __init__(self, *args, **kwargs):
        # department = kwargs.pop('department')
        
        super(TaskSelectForm, self).__init__(*args, **kwargs)
        (...)

I can call the form in my view with something like this: TaskSelectForm(request.GET) and it'll work fine. When i make a GET request the page loads and the fields are still filed.. Just as expected

However, i need the form to take an extra parameter, something like this TaskSelectForm(request.GET, department = department)

Problem is that for every GET request the form fields become empty. The form doesn't retain the values from the last request.

I want the form fields to keep the last values.. How can i achieve this?

I'll post the whole code below just to make sure i didn't mess up:

class TaskSelectForm(forms.Form):
    def __init__(self, *args, **kwargs):
        department = kwargs.pop('department')
        
        super(TaskSelectForm, self).__init__(*args, **kwargs)

        department_tasks = Task.objects.filter(department = department)
        distinct_cr = [(k['client_repr'], k['client_repr']) for k in department_tasks.values('client_repr').distinct()]
        distinct_td = [(k['task_description'], k['task_description']) for k in department_tasks.values('task_description').distinct()]
        distinct_us = [(x.id, (str(x))) for x in department.users.all()]

        for _ in [distinct_cr, distinct_td, distinct_us]:
            _.sort(key = lambda x: x[0])
            _.insert(0, ('', '---------'))
        
        self.fields['client_repr'] = forms.ChoiceField(choices = distinct_cr, required = False)
        self.fields['task_description'] = forms.ChoiceField(choices = distinct_td, required = False)
        self.fields['from'] = forms.DateField(widget = forms.DateInput())
        self.fields['to'] = forms.DateField(widget = forms.DateInput())
        self.fields['user'] = forms.ChoiceField(choices = distinct_us, required = False)

        for visible in self.visible_fields():
            visible.field.widget.attrs['class'] = 'form-control mb-3'

arcanemachine · Answer 1 · 2020-09-20T21:31:42.733

Use Sessions (included with Django).

You can save a variable on the server side, but store a reference to the variable on the client using a cookie. This allows you to preserve state for visitors while they are using your site.

You can temporarily save your data (and preserve it for the length of the user's session) using request.session, which is a dictionary. You can access request.session anywhere you have access to a request object:

request.session['your_field'] = form.cleaned_data['your_field']

When you are done with the data, you can delete the key:

del request.session['your_field']

To check for the existence of a session key without throwing a NameError if it doesn't exist:

request.session.get('your_field', '')

Per this StackOverflow answer, you need to call request.session.modified = True if using a nested key (e.g. request.session['your_field']['your_nested_field']), although this should not be a problem for your use case.

(Note that this requires the browser to have cookies enabled, which shouldn't be a problem for 99.9% of your visitors).

Thanks! Using sessions was definitely a possibility but i just realized i can use the initial property in the forms fields. Both good solutions — Ricardo Vilaça, Sep 21 '20 at 10:10
Gotcha, I thought you needed to store the request data before re-displaying the form. — arcanemachine, Sep 21 '20 at 21:59

score 1 · Accepted Answer · answered Sep 20 '20 at 21:37

1

Why don't you use initial?

Like f = ContactForm(initial={'subject': 'Hi there!'})?

Here is documentation - https://docs.djangoproject.com/en/3.1/ref/forms/api/#dynamic-initial-values

UPDATE: Or you can use form wizard - https://django-formtools.readthedocs.io/en/latest/wizard.html

answered Sep 20 '20 at 21:37

mrvol

2,575
18
21

1

That was it! I just needed to set the initial to the value of the passed request. Ex: self.fields['client_repr'].initial = request.get('client_repr') – Ricardo Vilaça Sep 21 '20 at 10:08

Keeping field values on Form fields after request.GET - but also passing other kwargs

2 Answers2