Django - ReverseManyToOneDescriptor' 对象没有属性 'all'

Question

我可以看到很多相关的问题，当我检查它们时，从我可以看到的代码应该工作的内容，但是我会遇到以下错误？

模型：

class Circuits(models.Model):    
    site_data = models.ForeignKey(SiteData,verbose_name="Site")   
    order_no = models.CharField(max_length=200,verbose_name="Order No")
    expected_install_date = models.DateField()
    install_date = models.DateField(blank=True,null=True)
    circuit_type = models.CharField(max_length=100,choices=settings.CIRCUIT_CHOICES)    
    circuit_preference = models.CharField(max_length=20,verbose_name="Circuit Preference",choices=settings.CIRCUIT_PREFERENCE,blank=True,null=True)
    circuit_speed = models.IntegerField(blank=True,null=True)
    circuit_bearer = models.IntegerField(blank=True,null=True)
class CircuitMaintenance(models.Model): 
    circuit = models.ForeignKey(Circuits,verbose_name="Circuit", related_name='maintenance')
    ref = models.CharField(max_length=200,verbose_name="Ref No")
    start_time = models.DateTimeField()
    end_time = models.DateTimeField()
    notes = models.TextField(blank=True,null=True)

错误

circuits = Circuits.objects.filter(site_data__id=1)
for i in Circuits.maintenance.all():
 print i
AttributeError: 'ReverseManyToOneDescriptor' object has no attribute 'all'

编辑：修改较低的情况C仍然遇到错误：

>>> from sites.models import Circuits
>>> circuits = Circuits.objects.filter(site_data__id=1)
>>> for i in circuits.maintenance.all():
...  print i
...
Traceback (most recent call last):
  File "<console>", line 1, in <module>
AttributeError: 'QuerySet' object has no attribute 'maintenance'
>>>

Answer 1

您需要使用变量circuits

circuits = Circuits.objects.filter(site_data__id=1)
for cm in circuits:
    maintenances = cm.maintenance.all()
    for maintenance in maintenances:
         print(maintenance )

如果您不定义related_name，则可以：

circuits.circuitmaintenance_set.all() :