有关middleware的错误
提出问题
在运行python manage.py makemigrations出现了错误，错误信息如下：
ERRORS:
?: (admin.E408) 'django.contrib.auth.middleware.AuthenticationMiddleware' must be in MIDDLEWARE in order to use the admin application.
?: (admin.E409) 'django.contrib.messages.middleware.MessageMiddleware' must be in MIDDLEWARE in order to use the admin application.
?: (admin.E410) 'django.contrib.sessions.middleware.SessionMiddleware' must be in MIDDLEWARE in order to use the admin application.
解决方法
之前我将MIDDLERWARE的内容全部注释掉了，然后加上了自己想要修改的内容，由于报错，因此我将上面三个取消注释，最后结果如下：
MIDDLEWARE = [
#'django.middleware.security.SecurityMiddleware',
'django.contrib.sessions.middleware.SessionMiddleware',
#'django.middleware.common.CommonMiddleware',
#'django.middleware.csrf.CsrfViewMiddleware',
'django.contrib.auth.middleware.AuthenticationMiddleware',
'django.contrib.messages.middleware.MessageMiddleware',
#'django.middleware.clickjacking.XFrameOptionsMiddleware',
'django.contrib.admin',
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.messages',
'django.contrib.staticfiles',
'myblog', #新建立的app
]
然后再尝试命令：
python manage.py makemigrations
成功运行。
有关model默认值的问题
提出问题
我之前的Shoes类是这样的：
class Shoes(models.Model):
# 球鞋表的创建
# 把id作为主键，考虑到后面网址的拼接id是str类型，
# 所以这里主键设置为charfiled
ShoesId=models.CharField(verbose_name='球鞋id',max_length=100,primary_key=True) #不要加default属性
title=models.CharField(verbose_name='球鞋title',max_length=100)
user=models.CharField(verbose_name='用户名称',max_length=100,default='root')
class Meta:
verbose_name = '球鞋id'
verbose_name_plural = verbose_name
def _str_(self):
return self.title
后来添加了一个属性叫number：
number=models.CharField(verbose_name='球鞋货号',max_length=100)
然后运行命令：python manage.py makemigrations
这个报出错误：
You are trying to add a non-nullable field 'number' to shoes without a default; we can't do that (the database needs something to populate existing rows).
Please select a fix:
1)Provide a one-off default now (will be set on all existing rows with a null value for this column)
2)Quit, and let me add a default in models.py
Select an option:
解决办法
这种问题的解决办法一般是，将新增的属性设置一个默认值即可：
number=models.CharField(verbose_name='球鞋货号',max_length=100,default=" ")
