Django：ManyToManyField未定义错误

Question

我一直在尝试编辑django-userena中的用户资料，其他部分都没问题，就是我的ManyToManyFields（多对多字段）出了点状况。我设置了以下模型：

class MyProfile(UserenaBaseProfile):
    user = models.OneToOneField(User,unique=True,  
                        verbose_name=_('user'),related_name='my_profile')
    favourite_snack = models.CharField(_('favourite snack'),max_length=5) 
    firstname = models.CharField(_('username'), max_length=55)
    lastname = models.CharField(_('lastname'), max_length=66)
    industry = models.CharField(_('industry'), max_length=190)
    occupation = models.CharField(_('occupation'), max_length=140)
    bio = models.TextField(_('bio'))
    phone = models.CharField(_('phone'), max_length=10)
    skills = models.ManyToManyField(Skills)
    Interests = models.ManyToManyField(Interests)
    website = models.URLField()

class Skills(models.Model):
    skillName = models.CharField(max_length=80)

class Interests(models.Model):
    interestName = models.CharField(max_length=140)

当我同步数据库时，出现了以下错误：

 File "/pathtodjango/bin/app/accounts/models.py", line 17, in MyProfile
    skills = models.ManyToManyField(Skills)
NameError: name 'Skills' is not defined

Answer 1

问题在于你在定义模型类 Skills 之前就引用了它。要注意，Python 不像 JavaScript 那样支持函数（类）提升。 所以你的代码应该像这样：

class Skills(models.Model):
    skillName = models.CharField(max_length=80)

class Interests(models.Model):
    interestName = models.CharField(max_length=140)


class MyProfile(UserenaBaseProfile):
    user = models.OneToOneField(User,unique=True,  
                        verbose_name=_('user'),related_name='my_profile')
    favourite_snack = models.CharField(_('favourite snack'),max_length=5) 
    firstname = models.CharField(_('username'), max_length=55)
    lastname = models.CharField(_('lastname'), max_length=66)
    industry = models.CharField(_('industry'), max_length=190)
    occupation = models.CharField(_('occupation'), max_length=140)
    bio = models.TextField(_('bio'))
    phone = models.CharField(_('phone'), max_length=10)
    skills = models.ManyToManyField(Skills)
    Interests = models.ManyToManyField(Interests)
    website = models.URLField()

Answer 2

使用懒引用：

skills = models.ManyToManyField('Skills')