Django选择带有空的对象ManyToManyField

Question

考虑到以下模型，了解一个家庭，如何选择没有买家的儿童？

class Family... 

class Kid(models.Model): 
    name = models.CharField(max_length=255) 
    family = models.ForeignKey(Family) 
    buyer = models.ManyToManyField(Buyer, blank=True, null=True) 

family = get_object_or_404(Family, pk=1) 
for_sale = family.kid_set.filter(buyer... this screws my child trade business 

Answer 1

family.kid_set.filter(buyer__isnull=True)应该工作。

Answer 2

@ piquadrat's answer是正确的。您可以也做：

for_sale = Kid.objects.filter(family__pk = 1, buyer = None) 

这可以让你避免一个单独的查询来查找Family实例。