Django ManytoManyfields 错误`AttributeError：'ManyRelatedManager'对象没有属性'dev_id'`

Question

我想已经有很多可用的讨论几乎已经完成了所有讨论，但仍然面临这个错误。

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class Device(models.Model):\n    """Storing Device ids """\n    platform  = models.CharField(max_length=3, choices=PLATFORM, default = \'ANR\')\n    dev_id    = models.CharField(max_length = 255, null=True, blank=False)\n\xe2\x80\x8b\n    def __str__(self):\n        return str(self.id)\n\n

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class UserProfile(models.Model):\n    user             = models.OneToOneField(\'user.User\', \n                                         on_delete=models.CASCADE,\n                                         related_name=\'profile\',\n                                         primary_key=True,\n                                         unique=True)\n    device           = models.ManyToManyField(Device, related_name=\'devices\')\n\xe2\x80\x8b\n    def __str__(self):\n        return str(self.user)\n

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错误1

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username = UserProfile.objects.filter(\n                    phone_number=user_username).get()\nusername.device.dev_id\n*** AttributeError: \'ManyRelatedManager\' object has no attribute \'dev_id\'\n\n\n

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错误 2\n经过一番研究

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\nusername.device.values_list(\'dev_id\', flat=True)\n<QuerySet []>\n\xe2\x80\x8b```\n\nThere is no device found with this user but there are devices in them for this username\nFor the reference, I have listed devices\n\n```python\n>>> Device.objects.all()\n<QuerySet [<Device: 1>]>\n

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错误3

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(Pdb) username.device.all()\n<QuerySet []>\n Checked with this Method but not able to list devices\n\n

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Answer 1

这是行不通的，因为这device是一种ManyToMany关系。显然，用户可以关联多个设备（或没有）。

如果您想访问某个用户的所有设备，请尝试以下操作：

user.device.all()

这将为您提供QuerySet来自 a 的RelatedManager。就像普通的一样使用它QuerySet：

for d in user.device.all():
  print(d.dev_id)

当然，文档中对此进行了描述。