django报错TypeError: __init__() missing 1 required positional argument: 'on_delete'

今天再练习django时报错django报错TypeError: __init__() missing 1 required positional argument: 'on_delete'

解决方法为在外键一项添加on_delete=models.CASCADE便可解决

class Buinesss(models.Model):
    caption = models.CharField(max_length=32)

class Host(models.Model):
    nid = models.AutoField(primary_key=True)
    hostname = models.CharField(max_length=32,db_index=True)
    ip = models.IPAddressField(db_index=True)
    port = models.IntegerField()
    b = models.ForeignKey(to="Business",to_field="id",on_delete=models.CASCADE)