問題：在執行python manage.py makemigrations learning_logs時，系統會報錯，提示：TypeError: __init__() missing 1 required positional argument: 'on_delete'
| (ll_env) c:\WorkSpace\SimpleTest\learning_log>python manage.py makemigrations learning_logs
Traceback (most recent call last):
File "manage.py", line 15, in <module>
execute_from_command_line(sys.argv)
File "c:\WorkSpace\SimpleTest\learning_log\ll_env\lib\site-packages\django\core\management\__init__.py", line 371, in execute_from_command_line
utility.execute()
File "c:\WorkSpace\SimpleTest\learning_log\ll_env\lib\site-packages\django\core\management\__init__.py", line 347, in execute
django.setup()
File "c:\WorkSpace\SimpleTest\learning_log\ll_env\lib\site-packages\django\__init__.py", line 24, in setup
apps.populate(settings.INSTALLED_APPS)
File "c:\WorkSpace\SimpleTest\learning_log\ll_env\lib\site-packages\django\apps\registry.py", line 112, in populate
app_config.import_models()
File "c:\WorkSpace\SimpleTest\learning_log\ll_env\lib\site-packages\django\apps\config.py", line 198, in import_models
self.models_module = import_module(models_module_name)
File "C:\python36\lib\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 "c:\WorkSpace\SimpleTest\learning_log\learning_logs\models.py", line 13, in <module>
class Entry(models.Model):
File "c:\WorkSpace\SimpleTest\learning_log\learning_logs\models.py", line 15, in Entry
topic = models.ForeignKey(Topic)
TypeError: __init__() missing 1 required positional argument: 'on_delete' |
代碼如下：
| from django.db import models # Create your models here.
class Topic(models.Model):
"""用戶學習的主題"""
text = models.CharField(max_length=200)
date_added = models.DateTimeField(auto_now_add=True)
def __str__(self):
"""返回模型的字符串表示"""
return self.text class Entry(models.Model):
"""學到的有關某個主題的具體知識"""
topic = models.ForeignKey(Topic)
text = models.TextField()
date_added = models.DateTimeField(auto_now_add=True)
class Meta:
verbose_name_plural = 'entries'
def __str__(self):
"""返回模型的字符串表示"""
return self.text[:50] + "..." |
解決辦法：修改指定外鍵的方式
| from django.db import models # Create your models here.
class Topic(models.Model):
"""用戶學習的主題"""
text = models.CharField(max_length=200)
date_added = models.DateTimeField(auto_now_add=True)
def __str__(self):
"""返回模型的字符串表示"""
return self.text class Entry(models.Model):
"""學到的有關某個主題的具體知識"""
topic = models.ForeignKey(Topic, on_delete=models.CASCADE)
text = models.TextField()
date_added = models.DateTimeField(auto_now_add=True)
class Meta:
verbose_name_plural = 'entries'
def __str__(self):
"""返回模型的字符串表示"""
return self.text[:50] + "..." |
