python - Django admin removes selected choice in ModelChoiceField on edit? -

i'm using admin.tabularinline in admin code i've made custom form.

class ratecardform(forms.modelform):     category = forms.modelchoicefield(queryset=models.category.objects.all(), label='category')      class meta:         model = models.ratecard         fields = ('category')  class ratecardinline(admin.tabularinline):     model = models.ratecard     form = ratecardform     = 3 

the problem after i've saved model instance, whenever edit model instance, remove pre-selected choice , i'll have select choice again. ideas how stop it?

also modelchoicefield if don't specify label, come none on admin page, don't need specify admin.stackedinline.

to preselect selected category instance can set primary key field's initial value overriding __init__() on modelform:

class ratecardform(forms.modelform):     category = forms.modelchoicefield(queryset=models.category.objects.all(), label='category')      class meta:         model = models.ratecard         fields = ('category')      def __init__(self, *args, **kwargs):         super(ratecardform, self).__init__(*args, **kwargs)         instance = kwargs.get('instance')         # instance none empty rows.         if instance:             selected_pk = # query primary key of selected category here             self.fields['category'].initial = selected_pk