问题：在执行python manage.py makemigrations learning_logs时，系统会报错，提示：TypeError: __init__() missing 1 required positional argument: 'on_delete'
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(ll_env) c:WorkSpaceSimpleTestlearning_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:WorkSpaceSimpleTestlearning_logll_envlibsite-packagesdjangocoremanagement\__init__.py", line 371, in execute_from_command_line
utility.execute()
File "c:WorkSpaceSimpleTestlearning_logll_envlibsite-packagesdjangocoremanagement\__init__.py", line 347, in execute
django.setup()
File "c:WorkSpaceSimpleTestlearning_logll_envlibsite-packagesdjango\__init__.py", line 24, in setup
apps.populate(settings.INSTALLED_APPS)
File "c:WorkSpaceSimpleTestlearning_logll_envlibsite-packagesdjangoapps
egistry.py", line 112, in populate
app_config.import_models()
File "c:WorkSpaceSimpleTestlearning_logll_envlibsite-packagesdjangoappsconfig.py", line 198, in import_models
self.models_module = import_module(models_module_name)
File "C:python36libimportlib\__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:WorkSpaceSimpleTestlearning_loglearning_logsmodels.py", line 13, in <module>
class Entry(models.Model):
File "c:WorkSpaceSimpleTestlearning_loglearning_logsmodels.py", line 15, in Entry
topic = models.ForeignKey(Topic)
TypeError: __init__() missing 1 required positional argument: 'on_delete'
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代码如下：
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from django.db import models
# Create your models here.
class Topic(models.Model):
"""用户学习的主题"""
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):
"""学到的有关某个主题的具体知识"""
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] + "..."
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解决办法：修改指定外键的方式
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from django.db import models
# Create your models here.
class Topic(models.Model):
"""用户学习的主题"""
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):
"""学到的有关某个主题的具体知识"""
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] + "..."
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