执行 python manage.py makemigrations 提示错误

Question

Traceback (most recent call last):
File "manage.py", line 23, in
main()
File "manage.py", line 19, in main
execute_from_command_line(sys.argv)
File "D:\codeProgram\python3.7\lib\site-packages\django\core\management__init__.py", line 381, in execute_from_command_line
utility.execute()
File "D:\codeProgram\python3.7\lib\site-packages\django\core\management__init__.py", line 357, in execute
django.setup()
File "D:\codeProgram\python3.7\lib\site-packages\django__init__.py", line 24, in setup
apps.populate(settings.INSTALLED_APPS)
File "D:\codeProgram\python3.7\lib\site-packages\django\apps\registry.py", line 114, in populate
app_config.import_models()
File "D:\codeProgram\python3.7\lib\site-packages\django\apps\config.py", line 211, in import_models
self.models_module = import_module(models_module_name)
File "D:\codeProgram\python3.7\lib\importlib__init__.py", line 127, in import_module
return bootstrap._gcd_import(name[level:], package, level)
File "", line 1006, in _gcd_import
File "", line 983, in _find_and_load
File "", line 967, in _find_and_load_unlocked
File "", line 677, in _load_unlocked
File "", line 728, in exec_module
File "", line 219, in _call_with_frames_removed
File "D:\codeStudy\django企业开发实战\typeidea\typeidea\blog\models.py", line 8, in
class Category(models.Model):
File "D:\codeStudy\django企业开发实战\typeidea\typeidea\blog\models.py", line 20, in Category
owner = models.ForeignKey(User, verbose_name="作者")
TypeError: __init_() missing 1 required positional argument: 'on_delete'

# -*- coding: utf-8 -*-
from __future__ import unicode_literals

from django.contrib.auth.models import User
from django.db import models


class Category(models.Model):
    STATUS_NORMAL = 1
    STATUS_DELETE = 0
    STATUS_ITEMS = (
        (STATUS_NORMAL, '正常'),
        (STATUS_DELETE, '删除'),
    )

    name = models.CharField(max_length=50, verbose_name="名称")
    status = models.PositiveIntegerField(
        default=STATUS_NORMAL, choices=STATUS_ITEMS, verbose_name="状态")
    is_nav = models.BooleanField(default=False, verbose_name="是否为导航")
    owner = models.ForeignKey(User, verbose_name="作者")
    created_time = models.DateTimeField(auto_now_add=True, verbose_name="创建时间")

    class Meta:
        verbose_name = verbose_name_plural = '分类'


class Tag(models.Model):
    STATUS_NORMAL = 1
    STATUS_DELETE = 0
    STATUS_ITEMS = (
        (STATUS_NORMAL, '正常'),
        (STATUS_DELETE, '删除'),
    )

    name = models.CharField(max_length=10, verbose_name="名称")
    status = models.PositiveIntegerField(
        default=STATUS_NORMAL, choices=STATUS_ITEMS, verbose_name="状态")
    owner = models.ForeignKey(User, verbose_name="作者")
    created_time = models.DateTimeField(auto_now_add=True, verbose_name="创建时间")

    class Meta:
        verbose_name = verbose_name_plural = '标签'


class Post(models.Model):
    STATUS_NORMAL = 1
    STATUS_DELETE = 0
    STATUS_DRAFT = 2
    STATUS_ITEMS = (
        (STATUS_NORMAL, '正常'),
        (STATUS_DELETE, '删除'),
        (STATUS_DRAFT, '草稿'),
    )

    title = models.CharField(max_length=255, verbose_name="标题")
    desc = models.CharField(max_length=1024, blank=True, verbose_name="摘要")
    content = models.TextField(verbose_name="正文", help_text="正文必须为MarkDown格式")
    status = models.PositiveIntegerField(
        default=STATUS_NORMAL, choices=STATUS_ITEMS, verbose_name="状态")
    category = models.ForeignKey(Category, verbose_name="分类")
    tag = models.ManyToManyField(Tag, verbose_name="标签")
    owner = models.ForeignKey(User, verbose_name="作者")
    created_time = models.DateTimeField(auto_now_add=True, verbose_name="创建时间")

    class Meta:
        verbose_name = verbose_name_plural = "文章"

Answer 1

django新版本中，如果有外键关联，必须要指定 on_delete=，on_delete是当删除关联表中的数据时，当前表与其关联的行的行为
可设置的值有

on_delete=None,             # 当删除关联表中的数据时，当前表与其关联的行的行为
                                        - models.CASCADE，删除关联数据，与之关联也删除
                                        - models.DO_NOTHING，删除关联数据，引发错误IntegrityError
                                        - models.PROTECT，删除关联数据，引发错误ProtectedError
                                        - models.SET_NULL，删除关联数据，与之关联的值设置为null（前提FK字段需要设置为可空）
                                        - models.SET_DEFAULT，删除关联数据，与之关联的值设置为默认值（前提FK字段需要设置默认值）
                                        - models.SET，删除关联数据，
                                                      a. 与之关联的值设置为指定值，设置：models.SET(值)
                                                      b. 与之关联的值设置为可执行对象的返回值，设置：models.SET(可执行对象)