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我有一个Position与模型相关的 ForeignKey 字段的Emplacement模型。在Emplacement我为Position.

我想要实现的是，当num_position在实例中修改字段时Emplacement，删除与该实例相关的位置并创建新的位置。

为此，我重写了Emplacement模型的save()方法并检查是否num_position已更改。

问题是Emplacement在修改其num_position字段后保存模型时，出现以下错误：

ValidationError: Select a valid choice. That choice is not one of the available choices.

我想这与位置的删除/重新创建有关，但我找不到原因。

怎么了？

模型.py

class Emplacement(models.Model): 

    num_position = models.IntegerField()
    # more fields

    __original_num_position = None

    def __init__(self, *args, **kwargs):
        super(Emplacement, self).__init__(*args, **kwargs)
        self.__original_num_position = self.num_position

    def save(self, *args, **kwargs):

        if self.num_position != self._Emplacement__original_num_position:
            # if num_position has changed, delete existing positions and recreate <num_position> positions
            Position.objects.filter(emplacement=self).delete()            
            for i in range(self.num_position):
                position = Position()
                position.emplacement = self
                position.number = i+1
                position.save()

        super(Emplacement, self).save(*args, **kwargs)

class Position(models.Model):
    emplacement = models.ForeignKey(Emplacement)
    number = models.IntegerField()

管理员.py

class PositionInline(admin.TabularInline):
    model = Position

class EmplacementAdmin(admin.ModelAdmin):
    inlines = [PositionInline]

my_site.register(Emplacement, EmplacementAdmin)

编辑

我也尝试了一个信号，但得到了同样的错误：

@receiver(post_save, sender=Emplacement)
def create_positions(sender, instance, created, **kwargs):
    """Create positions when num_position has changed."""
    if instance.num_position != instance.old_num_position:
        Position.objects.filter(emplacement=instance).delete()
        for i in range(instance.num_position):
            position = Position()
            position.emplacement = instance
            position.numero = i+1            
            position.save()
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1 回答 1

1

我遇到了完全相同的问题。最后通过不在模型端实现创建/删除逻辑而是在 Forms/FormSets 中解决它。

因此，在“主”管理类中，在您的情况下为“EmplacementAdmin”，扩展了 save_formset 方法：

def save_formset(self, request, form, formset, change):
    instance = form.instance
    deleted = []
    if instance and instance.__original_num_position != instance.num_position:
        ''' create new Positions if needed '''

        formset.delete_positions = None # pass on a list, QuerySet, whatever

    super(EmplacementAdmin, self).save_formset(request, form, formset, change)

并像这样创建一个 PositionFormSet：

class PositionFormSet(BaseInlineFormSet):
    delete_positions = []

    @property
    def deleted_forms(self):
        deleted_forms = []
        try:
            deleted_forms = super(PositionFormSet, self).deleted_forms
        except AttributeError:
            pass
        for form in self.forms:
            if form.instance in self.delete_positions:
                 deleted_forms.append(form)
        self.delete_positions = []
        return deleted_forms

并在您的 inlineadmin 中设置此表单集：

class PositionInline(admin.TabularInline):
    model = Position
    formset = PositionFormSet

不完全是我的想法，但这个技巧对我有用。很想知道是否有一些更优雅的解决方案:-)

于 2013-10-24T12:10:02.603 回答