Question

我正在创建一个测验应用程序，每个用户都可以在其中存储要提问的选项，并且我希望Choice模型作为模型Question的ForeignKey，但是在makemigrations时出现错误

模型：

class Choice(models.CharField):
    ans = models.CharField(max_length=50)
    def __str__(self):
        return self.ans
    class Meta:
        ordering = ['ans']    

class Question(models.Model):
    que = models.CharField(max_length=200)
    choice = models.ForeignKey(Choice,on_delete=models.CASCADE)
    def __str__(self):
        return self.que    
    class Meta:
        ordering = ['que']

错误：

(venv) bhupesh@Laptop:/home/mydata/challenges$ python manage.py makemigrations
Traceback (most recent call last):
  File "/home/mydata/challenges/venv/lib/python3.6/site-packages/django/db/models/fields/related.py", line 786, in __init__
    to._meta.model_name
AttributeError: type object 'Choice' has no attribute '_meta'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "manage.py", line 22, in <module>
    execute_from_command_line(sys.argv)
  File "/home/mydata/challenges/venv/lib/python3.6/site-packages/django/core/management/__init__.py", line 401, in execute_from_command_line
    utility.execute()
  File "/home/mydata/challenges/venv/lib/python3.6/site-packages/django/core/management/__init__.py", line 377, in execute
    django.setup()
  File "/home/mydata/challenges/venv/lib/python3.6/site-packages/django/__init__.py", line 24, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "/home/mydata/challenges/venv/lib/python3.6/site-packages/django/apps/registry.py", line 114, in populate
    app_config.import_models()
  File "/home/mydata/challenges/venv/lib/python3.6/site-packages/django/apps/config.py", line 211, in import_models
    self.models_module = import_module(models_module_name)
  File "/usr/lib/python3.6/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 994, in _gcd_import
  File "<frozen importlib._bootstrap>", line 971, in _find_and_load
  File "<frozen importlib._bootstrap>", line 955, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 665, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 678, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/home/mydata/challenges/quize/models.py", line 20, in <module>
    class Question(models.Model):
  File "/home/mydata/challenges/quize/models.py", line 22, in Question
    choice = models.ForeignKey(Choice,on_delete=models.CASCADE)
  File "/home/mydata/challenges/venv/lib/python3.6/site-packages/django/db/models/fields/related.py", line 792, in __init__
    RECURSIVE_RELATIONSHIP_CONSTANT,
AssertionError: ForeignKey(<class 'quize.models.Choice'>) is invalid. First parameter to ForeignKey must be either a model, a model name, or the string 'self'

Answer 1

您没有将Choice设为Model的子类，但是将CharField设为class Choice(models.CharField) class Choice(models.Model): ans = models.CharField(max_length=50) def __str__(self): return self.ans class Meta: ordering = ['ans']

Answer 2

您选择的课程有模型。CharField将其更改为此

class Choice(models.Model):
    ans = models.CharField(max_length=50)
    def __str__(self):
        return self.ans
    class Meta:
        ordering = ['ans']

Migrations for 'choice':
  choice\migrations\0001_initial.py
    - Create model Choice
    - Create model Question

无法在Django模型中创建ForeignKey

2 个答案: