说在我models.py我有以下几点: class Company(models.Model):
name = ...
class Rate(models.Model):
company = models.ForeignKey(Company)
name = ...
class Client(models.Model):
name = ...
我想验证提交的URL在数据库中不存在。 Form类看起来像这样的相关部分: from django.contrib.sites.models import Site
class SignUpForm(forms.Form):
# ... Other fields ...
url = forms.URLField(label='URL for new site, eg: exa