迭代字典時動態設置類屬性（模型字段）

Question

我正在嘗試根據字典中包含的鍵，值對動態定義模型的字段。

我嘗試了兩種方法：

字典是：

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

非常錯誤（因為未定義self而生成異常）：

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'

顯然錯誤但不創建模型字段：

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'

有可能做我想做的事嗎？ 我確定是的！

Answer 1

在定義類之后，您需要設置這些額外的屬性：

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))

您可以使用類裝飾器將for循環包裝到應用於該類的函數中：

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:
    # ...

我有點擔心Django元類處理要處理這些字段，您可能需要添加其他調用以使EmailNotification._meta結構知道您添加的其他字段。

Answer 2

你可以使用類裝飾器：

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

感謝答案中的建議，但有一個關鍵缺失的概念。

必須做兩件事：

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

一個有效的解決方案：

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