Django Forms - How to Use Prefix Parameter


Question

Say I have a form like:

class GeneralForm(forms.Form):
    field1 = forms.IntegerField(required=False)
    field2 = forms. IntegerField(required=False)

And I want to show it twice on a page within one form tag each time with a different prefix e.g.,:

rest of page ...
<form ..>
GeneralForm(data,prefix="form1").as_table()
GeneralForm(data,prefix="form2").as_table()
<input type="submit" />
</form>
rest of page ...

When the user submits this, how do I get the submitted form back into two separate forms to do validation, and redisplay it?

This was the only documentation I could find and it's peckish.

1
18
10/22/2008 4:10:03 PM

Accepted Answer

You process each form as you normally would, ensuring that you create instances which have the same prefixes as those used to generate the form initially.

Here's a slightly awkward example using the form you've given, as I don't know what the exact use case is:

def some_view(request):
    if request.method == 'POST':
        form1 = GeneralForm(request.POST, prefix='form1')
        form2 = GeneralForm(request.POST, prefix='form2')
        if all([form1.is_valid(), form2.is_valid()]):
            pass # Do stuff with the forms
    else:
        form1 = GeneralForm(prefix='form1')
        form2 = GeneralForm(prefix='form2')
    return render_to_response('some_template.html', {
        'form1': form1,
        'form2': form2,
    })

Here's some real-world sample code which demonstrates processing forms using the prefix:

http://collingrady.wordpress.com/2008/02/18/editing-multiple-objects-in-django-with-newforms/

31
10/22/2008 4:34:19 PM

Even better, I think formsets is exactly what you're looking for.

class GeneralForm(forms.Form):
    field1 = forms.IntegerField(required=False)
    field2 = forms. IntegerField(required=False)

from django.forms.formsets import formset_factory

# GeneralSet is a formset with 2 occurrences of GeneralForm 
# ( as a formset allows the user to add new items, this enforces
#   2 fixed items, no less, no more )
GeneralSet = formset_factory(GeneralForm, extra=2, max_num=2)

# example view

def someview(request):
    general_set = GeneralSet(request.POST)
    if general_set.is_valid():
        for form in general_set.forms:
            # do something with data
    return render_to_response("template.html", {'form': general_set}, RequestContext(request))

You can even have a formset automatically generated from a model with modelformset_factory , which are used by the automated django admin. FormSet handle even more stuff than simple forms, like adding, removing and sorting items.


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