django admin form with predefined inlines

Question

The problem is to have the inline models to have some of theirs fields preselected according to other model.

Let's make an example:

class Document(models.Model):
    DOC_TYPES = ((DC1, 'Doc type 1'), (DC2, 'Doc type 2'))
    doctype = model.CharField(choices=DOC_TYPES, default=DC1)

class OptionCategory(models.Model):
    name = model.CharField()

class Option(models.Model):
    document = models.ForeignKey(Document)
    option_category = models.ForeignKey(OptionCategory)
    some_data = models.CharField()

Assume that option is defined inline in document model admin.

OptionCategory is necessary - those may be added by admin - I'd like to have a creation form for Document with so many option models in inline forms as there is option categories. This can be achieved easily using extras in Option model admin. The questions are:

1. How to present inline fields each with different option category preselected?
2. How to change options dynamically (basing on Document.doctype after adding similar doctype field in OptionCategory) - preferably with ajax?

Answer 1

1. How to present inline fields each with different option type preselected:

models.py

    class DocType(models.Model):
        name = models.CharField(max_length=255)

        def __unicode__(self):
            return self.name


    class Document(models.Model):
        doc_type = models.ForeignKey(DocType)
        some_data = models.CharField(max_length=255)

        def __unicode__(self):
            return self.some_data


    class OptionType(models.Model):
        name = models.CharField(max_length=255)
        doc_type = models.ForeignKey(DocType)

        def __unicode__(self):
            return self.name


    class Option(models.Model):
        document = models.ForeignKey(Document)
        option_type = models.ForeignKey(OptionType)
        some_data = models.CharField(max_length=255)

        def __unicode__(self):
            return self.some_data

admin.py

 class InlineOption(admin.TabularInline):
    model = Option
    extra = 3

    initial = [
        {'some_data': 'init_val1', 'option_type': 1},
        {'some_data': 'init_val2'},
    ]

    create_from_default = True

    def get_formset(self, request, obj=None, **kwargs):
        initial = self.initial[:]

        class _Form(forms.ModelForm):
            form_initial = initial

            def __init__(self, *args, **kwargs):
                if len(self.form_initial) and not 'instance' in kwargs:
                    kwargs['initial'] = self.form_initial.pop(0)
                return super(_Form, self).__init__(*args, **kwargs)

        if self.create_from_default:
            if request.method == 'GET':
                self.form = _Form
            else:
                self.form = forms.ModelForm
        else:
            self.form = _Form

        return super(InlineOption, self).get_formset(request, obj, **kwargs)



class AdminDocument(admin.ModelAdmin):
    inlines = [InlineOption]