django form creation on init

How can I add a field in the form init function? e.g. in the code below I want to add a profile field.

class StaffForm(forms.ModelForm):
    def __init__(self, user, *args, **kwargs):
      开发者_如何学JAVA  if user.pk == 1:
            self.fields['profile'] = forms.CharField(max_length=200)

        super(StaffForm, self).__init__(*args, **kwargs)

    class Meta:
        model = Staff

I know I can add it just below the class StaffForm.... line but I want this to be dynamic depending on what user is passed in so can't do it this way.

Thanks

Just need to switch the init function round so that super is called before adding anymore fields.

class StaffForm(forms.ModelForm):
    def __init__(self, user, *args, **kwargs):
        super(StaffForm, self).__init__(*args, **kwargs)

        if user.pk == 1:
            self.fields['profile'] = forms.CharField(max_length=200)
            self.fields['profile'].initial = 'whatever you want'
    class Meta:
        model = Staff