Question

我试图根据字典中包含的键，值对动态定义模型的字段。

我尝试过两种方式：

字典是：

NOTIFICATION_TYPES = {
    'friend_request_received': 0,
    'friend_request_accepted': 1,
    # eccetera
}

非常错误（因为未定义self而生成异常）：

class EmailNotification(models.Model):
    """
    User Email Notification Model
    Takes care of tracking the user's email notification preferences
    """
    user = models.OneToOneField(User, verbose_name=_('user'))

    for key, value in NOTIFICATION_TYPES.items():
        setattr(self, key, models.BooleanField(_('notify new matches'), default=True))

    class Meta:
        db_table = 'profile_email_notification'

显然错误但不会创建模型字段：

class EmailNotification(models.Model):
    """
    User Email Notification Model
    Takes care of tracking the user's email notification preferences
    """
    user = models.OneToOneField(User, verbose_name=_('user'))

    def __init__(self, *args, **kwargs):

        for key, value in NOTIFICATION_TYPES.items():
            setattr(self.__class__, key, models.BooleanField(_(key), default=True))

        super(EmailNotification, self).__init__(*args, **kwargs)

    class Meta:
        db_table = 'profile_email_notification'

我可以做我想做的事情吗？我确定是的！

Answer 1

在定义类之后，您需要设置的额外属性：

class EmailNotification(models.Model): """ User Email Notification Model Takes care of tracking the user's email notification preferences """ user = models.OneToOneField(User, verbose_name=_('user')) class Meta: db_table = 'profile_email_notification' for key, value in NOTIFICATION_TYPES.items(): setattr(EmailNotification, key, models.BooleanField(_('notify new matches'), default=True))

您可以使用class decorator将for循环包装到应用于类的函数中：

def add_notification(cls): for key, value in NOTIFICATION_TYPES.items(): setattr(cls, key, models.BooleanField(_('notify new matches'), default=True)) return cls @add_notification class EmailNotification: # ...

我有点担心Django元类处理会想要处理这些字段，您可能需要添加其他调用以使EmailNotification._meta结构知道您添加的其他字段。

Answer 2

您可以使用类装饰器：

def add_notification(cls):
    for key in NOTIFICATION_TYPES:
        setattr(cls, key, models.BooleanField(_('notify new matches'), default=True))
    return cls

@add_notification
class EmailNotification(models.Model):
    """
    User Email Notification Model
    Takes care of tracking the user's email notification preferences
    """
    user = models.OneToOneField(User, verbose_name=_('user'))

    class Meta:
        db_table = 'profile_email_notification'

Answer 3

感谢答案中的建议，但有一个关键缺失的概念。

必须做两件事：

setattr(myclass, key, field)
myclass.add_to_class(key, field)

这里有一个有效的解决方案：

https://github.com/nemesisdesign/nodeshot/blob/7798f81d558791499039afab1c860483fe30dd77/nodeshot/community/notifications/models/user_settings.py#L6

迭代字典时动态设置类属性（模型字段）

3 个答案: