我正在尝试创建一个FilteredSelectMultiple，类似于用户端Django Admin中的组/权限分配。我设法使界面小部件已经显示（每个角色有5个）。但是我不确定后端逻辑。我目前正在为此使用FormView。我想知道：
我的想法是有两个列表：一个包含所有已保存到数据库中的记录（下次用户输入时应显示在选定内容中的项目），另一个是后一个最新列表。用户保存（它包含较新的元素和/或可能删除了一些旧元素）。但是我不确定这是正确的还是有更好的方法。
这些是我的代码（预先致歉，views.py尚不完整，因此目前使用打印）：
forms.py：
class DesignationForm(forms.ModelForm):
class Media:
css = {
'all': ('admin/css/responsive.css', 'admin/css/base.css', 'admin/css/widgets.css',)
}
js = ('/admin/jsi18n',)
class Meta:
model = Designations
fields = ['module_coordinator', 'instructor', 'moderator', 'verifier', 'invigilator']
module_coordinator = forms.ModelMultipleChoiceField(queryset=Staffs.objects.all(),
widget=FilteredSelectMultiple("Module Coordinator",
is_stacked=False),
required=False,
label="")
instructor = forms.ModelMultipleChoiceField(queryset=Staffs.objects.all(),
widget=FilteredSelectMultiple("Instructor",
is_stacked=False),
required=False,
label="")
moderator = forms.ModelMultipleChoiceField(queryset=Staffs.objects.all(),
widget=FilteredSelectMultiple("Moderator",
is_stacked=False),
required=False,
label="")
verifier = forms.ModelMultipleChoiceField(queryset=Staffs.objects.all(),
widget=FilteredSelectMultiple("Verifier",
is_stacked=False),
required=False,
label="")
invigilator = forms.ModelMultipleChoiceField(queryset=Staffs.objects.all(),
widget=FilteredSelectMultiple("invigilator",
is_stacked=False),
required=False,
label="")
views.py：
class DesignationsView(FormView):
form_class = DesignationForm
template_name = 'curricula/designations.html'
def form_valid(self, form):
# We need a before list for each role (Get this from the database since it already exists)
# Module Coordinator
already_chosen_mc = Designations.objects.filter(role__role_name='Module Coordinator',
curriculum__course_period__course__course_abbreviation=self.kwargs.get(
'course_abbr'),
curriculum__module_period__module__module_abbreviation=self.kwargs.get(
'module_abbr'),
curriculum__course_period__period__academic_year=self.kwargs.get(
'year'),
curriculum__course_period__period__semester=self.kwargs.get(
'semester'),
curriculum__stage=self.kwargs.get('stage')).values_list(
'staff__staff_id', flat=True)
print(already_chosen_mc)
# Instructor
already_chosen_instructor = Designations.objects.filter(role__role_name='Instructor',
curriculum__course_period__course__course_abbreviation=self.kwargs.get(
'course_abbr'),
curriculum__module_period__module__module_abbreviation=self.kwargs.get(
'module_abbr'),
curriculum__course_period__period__academic_year=self.kwargs.get(
'year'),
curriculum__course_period__period__semester=self.kwargs.get(
'semester'),
curriculum__stage=self.kwargs.get('stage')).values_list(
'staff__staff_id', flat=True)
print(already_chosen_instructor)
# Moderator
already_chosen_moderator = Designations.objects.filter(role__role_name='Moderator',
curriculum__course_period__course__course_abbreviation=self.kwargs.get(
'course_abbr'),
curriculum__module_period__module__module_abbreviation=self.kwargs.get(
'module_abbr'),
curriculum__course_period__period__academic_year=self.kwargs.get(
'year'),
curriculum__course_period__period__semester=self.kwargs.get(
'semester'),
curriculum__stage=self.kwargs.get('stage')).values_list(
'staff__staff_id', flat=True)
print(already_chosen_moderator)
# Verifier
already_chosen_verifier = Designations.objects.filter(role__role_name='Verifier',
curriculum__course_period__course__course_abbreviation=self.kwargs.get(
'course_abbr'),
curriculum__module_period__module__module_abbreviation=self.kwargs.get(
'module_abbr'),
curriculum__course_period__period__academic_year=self.kwargs.get(
'year'),
curriculum__course_period__period__semester=self.kwargs.get(
'semester'),
curriculum__stage=self.kwargs.get('stage')).values_list(
'staff__staff_id', flat=True)
print(already_chosen_verifier)
# Invigilator
already_chosen_invigilator = Designations.objects.filter(role__role_name='Invigilator',
curriculum__course_period__course__course_abbreviation=self.kwargs.get(
'course_abbr'),
curriculum__module_period__module__module_abbreviation=self.kwargs.get(
'module_abbr'),
curriculum__course_period__period__academic_year=self.kwargs.get(
'year'),
curriculum__course_period__period__semester=self.kwargs.get(
'semester'),
curriculum__stage=self.kwargs.get(
'stage')).values_list(
'staff__staff_id', flat=True)
print(already_chosen_invigilator)
# Now, we get the current lists, this lists contains both exist in, newly added
# and may have missing staffs, if they have been removed
# Module Coordinator
chosen_mc = self.request.POST.getlist('module_coordinator')
print(chosen_mc)
# Instructor
chosen_instructor = self.request.POST.getlist('instructor')
print(chosen_instructor)
# Moderator
chosen_moderator = self.request.POST.getlist('moderator')
print(chosen_moderator)
# Verifier
chosen_verifier = self.request.POST.getlist('verifier')
print(chosen_verifier)
# Invigilator
chosen_invigilator = self.request.POST.getlist('invigilator')
print(chosen_invigilator)
# At this point, we now have two lists for each designations. One before the save, and
# one after. Compare the two and find the differences
# between the two lists. Either staff(s) are removed or added.
# If the staffs in before and after matches, ignore
# Firstly, check if the before list is empty (no records found in DB)
# If the old list is empty, we know the after list are new elements to be added
# into the db
if not already_chosen_mc:
print("I am empty! Feed me!")
# Else if the old element has elements, check if the new lists elements have some that are newly included and/or removed (Unsure of how to do this)
非常感谢！