Django模型在后台的验证

Question

这段内容提到了一些关于模型和字段验证的事情，类似于clean()方法在模型和字段验证中的应用，还有Django管理后台的验证错误（不过这个问题比较老，那个时候模型验证还不存在）。

我想用模型验证来让我的代码更简洁，但我遇到了一个奇怪的错误。我的模型是这样的：

from django.db import models
from django.core.exceptions import ValidationError
from django.utils.translation import ugettext as _

class Period(models.Model):
    class Meta:
        app_label = 'nps'

    name = models.CharField(max_length=40)
    start = models.DateField()
    end = models.DateField()

    def clean(self):
        if self.start > self.end:
            raise ValidationError(
                _("Start date must be before end date"),
                code='invalid',
            )
        super(Period, self).clean()

    def validate_unique(self, exclude=None):
        conflicts = Period.objects.filter(
            start__lte=self.end,
            end__gte=self.start,
        )
        if any(conflicts):
            raise ValidationError(
                _("Periods may not overlap."),
                code='invalid',
            )
        super(Period, self).validate_unique(exclude)

    def __unicode__(self):
        return "%s (%s - %s)" % (self.name, self.start.strftime('%m/%d/%Y') or None, self.end.strftime('%m/%d/%Y') or None)

当我尝试保存一个无效的模型（比如开始日期在结束日期之后）时，我本以为会在管理页面看到一个验证错误，但实际上我得到了以下异常：

AttributeError at /admin/nps/period/add/
'ValidationError' object has no attribute 'error_dict'
Request Method: POST
Request URL:    http://localhost:8000/admin/nps/period/add/
Django Version: 1.6.2
Exception Type: AttributeError
Exception Value:    
'ValidationError' object has no attribute 'error_dict'
Exception Location: /opt/django_venv/local/lib/python2.7/site-packages/django/forms/models.py in _update_errors, line 327
Python Executable:  /opt/django_venv/bin/python
Python Version: 2.7.3
Python Path:    
['/opt/webapp',
 '/home/vagrant/.pycharm_helpers/pydev',
 '/opt/webapp',
 '/vagrant',
 '/opt/webapp/C',
 '/Program Files (x86)/JetBrains/PyCharm 3.1.1/plugins/sass/lib/stubs/sass_functions.scss',
 '/Python27',
 '/opt/django_venv/lib/python2.7',
 '/opt/django_venv/lib/python2.7/plat-linux2',
 '/opt/django_venv/lib/python2.7/lib-tk',
 '/opt/django_venv/lib/python2.7/lib-old',
 '/opt/django_venv/lib/python2.7/lib-dynload',
 '/usr/lib/python2.7',
 '/usr/lib/python2.7/plat-linux2',
 '/usr/lib/python2.7/lib-tk',
 '/opt/django_venv/local/lib/python2.7/site-packages',
 '/opt/webapp/webapp']
Server time:    Tue, 8 Apr 2014 16:29:24 -0400

看起来管理模板期待的不是一个ValidationError。我是不是做错了什么，还是说这是Django的一个bug？完整的错误信息可以在这里找到：https://gist.github.com/DBell-Feins/10170544

谢谢！

Answer 1

我之前也遇到过这个问题，经过一些尝试和错误后找到了解决办法。我在full_clean这个方法里加了以下内容，不过在其他地方也应该能用。

from django.core.exceptions import ValidationError
from django.core.exceptions import NON_FIELD_ERRORS

class User(models.Model):
    # ...
    def full_clean(self, *args, **kwargs):
        self.update_username_slug()

        if User.objects.filter(username_slug=self.username_slug).exclude(id=self.id).exists():
            raise ValidationError({
                'username': [
                    ValidationError(
                        message='Username already exists',
                        code='unique',
                        params={},
                    )
                ]
            })
        super(User, self).full_clean(*args, **kwargs)

所以在你的情况下，你可能需要像这样做。

class Period(models.Model):
    # ...
    def clean(self):
        if self.start > self.end:
            raise ValidationError({
                'start': [
                    ValidationError(
                        message=_("Start date must be before end date"),
                        code='invalid',
                        params={},
                    )
                ]
            })
        super(Period, self).clean()