.

rapids/forms.py

@@ -131,9 +131,31 @@ class RapidForm(ModelForm):
         instance = ModelForm.save(self, False)
         instance.save()
 
-        for exam in self.cleaned_data["exams"]:
-            exam.exam_questions.add(instance)
+        old_exams = instance.exams
 
+        new_exams = self.cleaned_data["exams"]
+
+        for exam in old_exams:
+            if exam in new_exams:
+                exam.exam_questions.add(instance)
+            else:
+                exam.exam_questions.remove(instance)
+
+        #        # Prepare a 'save_m2m' method for the form,
+        #        old_save_m2m = self.save_m2m
+        #
+        #        def save_m2m():
+        #            old_save_m2m()
+        #            # This is where we actually link the pizza with toppings
+        #            instance.exams.clear()
+        #            for exam in self.cleaned_data["exams"]:
+        #                instance.exams.add(exam)
+        #
+        #        self.save_m2m = save_m2m
+        #
+        #        # Do we need to save all changes now?
+        #        # if commit:
+        #        instance.save()
         self.save_m2m()
 
         return instance