对 m2m(多对多)字段的 django pre_save 验证

Question

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我正在尝试对带有 m2m 字段的 django rest 模型进行验证。我有一个分配有角色的模型。如果角色与现有模型重叠并且想抛出验证错误，我有一些逻辑。我已经尝试过 pre_save 信号，但显然 django 直到保存后才分配 m2m(无 ID)。如何访问数据 pre_save？这是模型:

class ActivityFactory (models.Model):
"""
This provides an interval over which ActivityDemands are auto-generated and ActivityStudyHours (note that activity study hours can be obsolete as all of the same information is already stored here) instead of the traditional method of inputing ActivityDemands per month.  The product of Activity and ActivityDemand will still create StudySiteWorkloads.
"""
start_date = models.DateField()
end_date = models.DateField()
hours = models.DecimalField(max_digits=5, decimal_places=2)
notes = models.TextField(blank=True, null=True)

activity = models.ForeignKey(Activity, on_delete=models.CASCADE, related_name='activity_factories')
roles = models.ManyToManyField(Role, blank=True, related_name='activity_factories')
study = models.ForeignKey(Study, on_delete=models.CASCADE, related_name="activity_factories")
trend_curve = models.ForeignKey(TrendCurve, on_delete=models.CASCADE, related_name="activity_factories")
slug = AutoSlugField(populate_from='study', db_index=True, unique=True, null=True)

class Meta:
    verbose_name_plural = 'Activity Factories'

def __str__(self):
    return "%s: %s : %s" % (self.study.study_name, self.activity.activity_name, self.trend_curve.denominator_name)

这是 pre_save:

@receiver(pre_save, sender=ActivityFactory)
def validate_factory(sender, instance, **kwargs):
queryset = ActivityFactory.objects.filter(activity=instance.activity, study=instance.study)
roles=instance.roles.objects.all()
for activity_factory in queryset:
    if activity_factory.slug!=instance.slug:
        if ((activity_factory.start_date <= instance.start_date <= activity_factory.end_date) or (activity_factory.start_date >= instance.end_date >= activity_factory.end_date)) and bool(set(activity_factory.roles.all()) & set(roles)):
            raise serializers.ValidationError({'activity':'Date intervals cannot overlap for a given activity in the same study with the same assigned role'}, code=400)
        if activity_factory.activity==instance.activity and activity_factory.hours!=instance.hours and bool(set(activity_factory.roles.all()) & set(roles)):
            raise serializers.ValidationError({'activity':'The same activity can not have differing hours assigned to the same role within a study. Consider a new activity or keep hours the same'}, code=400)

Answer 1

我想我可能已经弄明白了。您可以按如下方式使用 m2m_changed 信号:

@receiver(m2m_changed, sender=ActivityFactory.roles.through)
def validate_factory_m2m(sender, instance, **kwargs):
queryset = ActivityFactory.objects.filter(activity=instance.activity, study=instance.study)
roles=instance.roles.all()
for activity_factory in queryset:
    if activity_factory.slug!=instance.slug:
        if ((activity_factory.start_date <= instance.start_date <= activity_factory.end_date) or (activity_factory.start_date >= instance.end_date >= activity_factory.end_date)) and bool(set(activity_factory.roles.all()) & set(roles)):
            instance.delete()
            raise serializers.ValidationError({'activity':'Date intervals cannot overlap for a given activity with the same assigned role. Consider removing that role or changing the dates or activity'}, code=400)
        if activity_factory.activity==instance.activity and activity_factory.hours!=instance.hours and bool(set(activity_factory.roles.all()) & set(roles)):
            raise serializers.ValidationError({'activity':'The same activity can not have differing hours assigned to the same role within a study. Consider a new activity or role, or keep hours the same'}, code=400)