Django rest framework 返回错误信息 __str__ returned non-string (type NoneType)

问题如下

解决方法：

方法1.点击右上角的admin，把帐号退掉,然后在进入对应页面就可以了

方法2.不退出admin账号的话，我们看到在自己写的users模型中 替换了django自带的AbstractUser，然后又设置了name可以为空,所以返回non-string

在str的函数中,将返回值设置成AbstractUser里面的username就好了

apps.users.models源码：

from django.contrib.auth.models import AbstractUser

class UserProfile(AbstractUser):
    """
    用户
    """
    # CharField 一定要加max_length参数，说明这个字段的最大长度
    name = models.CharField(max_length=30, null=True, blank=True, verbose_name="姓名")
    birthday = models.DateField(null=True, blank=True, verbose_name="出生年月")
    gender = models.CharField(max_length=6, choices=(("male", u"男"),("female", u"女")),default="female", verbose_name="性别")
    mobile = models.CharField(max_length=11, verbose_name="电话")
    email = models.EmailField(max_length=100, null=True, blank=True, verbose_name="邮箱")

    class Mate:
        verbose_name = "用户"
        verbose_name_plural = verbose_name

    def __str__(self):
        return self.username

django.contrib.auth.models.AbstractUser源码：

class AbstractUser(AbstractBaseUser, PermissionsMixin):
    """
    An abstract base class implementing a fully featured User model with
    admin-compliant permissions.

    Username and password are required. Other fields are optional.
    """
    username_validator = UnicodeUsernameValidator() if six.PY3 else ASCIIUsernameValidator()

username = models.CharField(
    _('username'),
    max_length=150,
    unique=True,
    help_text=_('Required. 150 characters or fewer. Letters, digits and @/./+/-/_ only.'),
    validators=[username_validator],
    error_messages={
        'unique': _("A user with that username already exists."),
    },
)