djadhere/adhesions/forms.py

from django import forms
from django.forms import widgets
from django.utils.safestring import mark_safe

from .models import Adherent


class StringWidget(widgets.Input):
    def render(self, name, value, attrs=None):
        # Create a hidden field first
        hidden_field = widgets.HiddenInput(attrs)
        return mark_safe(u'%s %s' % (value, hidden_field.render(value, attrs)))


class AdherentForm(forms.ModelForm):
    adherent_id = forms.CharField(disabled=True, label='Numéro d’adhérent')

    class Meta:
        model = Adherent
        exclude = ()

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        if self.instance.id:
            self.fields['adherent_id'].initial = self.instance.id
        else:
            self.fields['adherent_id'].initial = 'Veuillez sauvegarder pour obtenir un numéro d’adhérent.'
            self.fields['adherent_id'].widget = StringWidget()

    def has_changed(self):
        return True