improve bda inscription form/view code

bda/forms.py

@@ -1,14 +1,42 @@
 # -*- coding: utf-8 -*-
 
-from __future__ import division
-from __future__ import print_function
-from __future__ import unicode_literals
-
 from django import forms
+from django.forms.models import BaseInlineFormSet
 from django.utils import timezone
+
 from bda.models import Attribution, Spectacle
 
 
+class InscriptionInlineFormSet(BaseInlineFormSet):
+
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+
+        # self.instance is a Participant object
+        tirage = self.instance.tirage
+
+        # set once for all "spectacle" field choices
+        # - restrict choices to the spectacles of this tirage
+        # - force_choices avoid many db requests
+        spectacles = tirage.spectacle_set.select_related('location')
+        choices = [(sp.pk, str(sp)) for sp in spectacles]
+        self.force_choices('spectacle', choices)
+
+    def force_choices(self, name, choices):
+        """Set choices of a field.
+
+        As ModelChoiceIterator (default use to get choices of a
+        ModelChoiceField), it appends an empty selection if requested.
+
+        """
+        for form in self.forms:
+            field = form.fields[name]
+            if field.empty_label is not None:
+                field.choices = [('', field.empty_label)] + choices
+            else:
+                field.choices = choices
+
+
 class TokenForm(forms.Form):
     token = forms.CharField(widget=forms.widgets.Textarea())