Django的相同型号的误差范围内引用ManyToManyField中没有报价
问题描述:
https://docs.djangoproject.com/en/1.11/topics/db/examples/many_to_many/Django的相同型号的误差范围内引用ManyToManyField中没有报价
所以,我根据我的代码关闭这个文件和我打了一个错误。
from django.db import models
class Gift(models.Model):
name = models.CharField(
max_length=120, unique=True, help_text='Enter the gift item name'
)
# skipping to the ManyToMany ....
genre = models.ManyToManyField(Category)
class Category(models.Model):
# skipping stuff like CATEGORIES ...
type = models.IntegerField(
primary_key = True, choices = CATEGORIES, default = EVENT,
)
description = models.CharField(max_length=500, null=True, blank=True)
我收到此错误
Traceback (most recent call last):
File "manage.py", line 22, in <module>
execute_from_command_line(sys.argv)
File "/.../gifting_db/lib/python3.6/site-packages/django/core/management/__init__.py", line 363, in execute_from_command_line
utility.execute()
File "/.../gifting_db/lib/python3.6/site-packages/django/core/management/__init__.py", line 337, in execute
django.setup()
File "/.../gifting_db/lib/python3.6/site-packages/django/__init__.py", line 27, in setup
apps.populate(settings.INSTALLED_APPS)
File "/.../gifting_db/lib/python3.6/site-packages/django/apps/registry.py", line 108, in populate
app_config.import_models()
File "/.../gifting_db/lib/python3.6/site-packages/django/apps/config.py", line 202, in import_models
self.models_module = import_module(models_module_name)
File "/.../gifting_db/lib/python3.6/importlib/__init__.py", line 126, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
File "<frozen importlib._bootstrap>", line 978, in _gcd_import
File "<frozen importlib._bootstrap>", line 961, in _find_and_load
File "<frozen importlib._bootstrap>", line 950, in _find_and_load_unlocked
File "<frozen importlib._bootstrap>", line 655, in _load_unlocked
File "<frozen importlib._bootstrap_external>", line 678, in exec_module
File "<frozen importlib._bootstrap>", line 205, in _call_with_frames_removed
File "/.../gifting_db/gifting/gifts/models.py", line 5, in <module>
class Gift(models.Model):
File "/.../gifting_db/gifting/gifts/models.py", line 20, in Gift
category = models.ManyToManyField(Category)
NameError: name 'Category' is not defined
但是,如果我添加报价到 '类别' 它的工作原理。任何想法为什么? django doc示例在“发布”和“文章”之间不使用引用https://docs.djangoproject.com/en/1.11/topics/db/examples/many_to_many/。如果有的话,我猜想我把'Category'放在一个字符串中,而不是对Category对象的引用?
genre = models.ManyToManyField('Category')
答
您的问题是Category
是直到Gift
之后定义。如果你想使用它没有引号,你需要将Category
放在Gift
以上。否则,报价工作正常,并提供相同的功能。
https://docs.djangoproject.com/en/dev/ref/models/fields/#foreignkey
如果你需要创建一个尚未被 定义的模型的关系,您可以使用该模型的名称,而不是模型 对象本身:
答
您需要在Gift
之前定义Category
或使用引号。
from django.db import models
class Category(models.Model):
# skipping stuff like CATEGORIES ...
type = models.IntegerField(
primary_key = True, choices=CATEGORIES, default=EVENT)
description = models.CharField(max_length=500, null=True, blank=True)
class Gift(models.Model):
name = models.CharField(max_length=120, unique=True, help_text='Enter the gift item name'
)
# skipping to the ManyToMany ....
genre = models.ManyToManyField(Category)
或者use quotes
from django.db import models
class Gift(models.Model):
name = models.CharField(max_length=120, unique=True, help_text='Enter the gift item name'
)
# skipping to the ManyToMany ....
genre = models.ManyToManyField('Category')
class Category(models.Model):
# skipping stuff like CATEGORIES ...
type = models.IntegerField(primary_key=True, choices=CATEGORIES, default=EVENT,)
description = models.CharField(max_length=500, null=True, blank=True
啊,这就是为什么它的报价工作。真棒谢谢你,我错过了在外键部分。 – myaddresstoday