代码：
from django.db import models
class Blog(models.Model):
name = models.CharField(max_length=100)
tagline = models.TextField()
def __unicode__(self): # __str__ on Python 3
return self.name
class Author(models.Model):
name = models.CharField(max_length=50)
email = models.EmailField()
def __unicode__(self): # __str__ on Python 3
return self.name
class Entry(models.Model):
blog = models.ForeignKey(Blog)
headline = models.CharField(max_length=255)
body_text = models.TextField()
pub_date = models.DateField()
mod_date = models.DateField()
authors = models.ManyToManyField(Author)
n_comments = models.IntegerField()
n_pingbacks = models.IntegerField()
rating = models.IntegerField()
def __unicode__(self): # __str__ on Python 3
return self.headline
执行报错如下：
Traceback (most recent call last):
File "manage.py", line 15, in <module>
execute_from_command_line(sys.argv)
File "E:\diango\venv\lib\site-packages\django\core\management\__init__.py", line 371, in execute_from_command_line
utility.execute()
File "E:\diango\venv\lib\site-packages\django\core\management\__init__.py", line 347, in execute
django.setup()
File "E:\diango\venv\lib\site-packages\django\__init__.py", line 24, in setup
apps.populate(settings.INSTALLED_APPS)
File "E:\diango\venv\lib\site-packages\django\apps\registry.py", line 112, in populate
app_config.import_models()
File "E:\diango\venv\lib\site-packages\django\apps\config.py", line 198, in import_models
self.models_module = import_module(models_module_name)
File "E:\Program Files\Anaconda3\lib\importlib\__init__.py", line 126, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
File "<frozen importlib._bootstrap>", line 986, in _gcd_import
File "<frozen importlib._bootstrap>", line 969, in _find_and_load
File "<frozen importlib._bootstrap>", line 958, in _find_and_load_unlocked
File "<frozen importlib._bootstrap>", line 673, in _load_unlocked
File "<frozen importlib._bootstrap_external>", line 665, in exec_module
File "<frozen importlib._bootstrap>", line 222, in _call_with_frames_removed
File "E:\diango\blog\models.py", line 24, in <module>
class Entry(models.Model):
File "E:\diango\blog\models.py", line 25, in Entry
blog = models.ForeignKey(Blog)
TypeError: __init__() missing 1 required positional argument: 'on_delete'
解决办法：
将有ForeignKey的代码改为：
blog = models.ForeignKey(Blog,on_delete=models.CASCADE,)
即在外键值的后面加上 on_delete=models.CASCADE
