django - Django m2m_changed 未通过自定义模型触发

Question

class SparePart(models.Model):
    name = models.CharField(max_length=255)
    description = models.TextField(blank=True, null=True)

class SparePartOrderRelation(models.Model):
    sparepart = models.ForeignKey(SparePart)
    order = models.ForeignKey('SparePartOrder')

class SparePartOrder(models.Model):
    spareparts = models.ManyToManyField(SparePart, through=SparePartOrderRelation)

def signaltest(**kwargs):
    print kwargs['action']

m2m_changed.connect(signaltest, sender=SparePartOrder.spareparts.through, weak=False, dispatch_uid='signaltest')

（为清楚起见，简化模型）

为什么不m2m_changed发送和signaltest调用信号？当我保存一个SparePartOrder？我已经尝试用对 m2m 模型（等）sender=的（可能的）引用的几乎所有组合替换SparePartOrder.sparepartsSparePartOrderRelation

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干杯