django - 类型错误 : __init__() got an unexpected keyword argument 'on_delete'

Question

我建立了一个模型:

class Channel(models.Model):
    title = models.CharField(max_length=255, unique=True)
    slug = models.SlugField(allow_unicode=True, unique=True)
    description = models.TextField(blank=True, default='')
    description_html = models.TextField(editable=False, default='', 
blank=True)
    subscribers = models.ManyToManyField(User, 
through="ChannelMembers", on_delete=models.CASCADE,)

当我做 makemigration 它说:

TypeError: __init__() got an unexpected keyword argument 'on_delete'

当删除 on_delete 它说:

TypeError: __init__() missing 1 required positional argument: 'on_delete'

穿什么？

Answer 1

on_delete 不是 ManyToManyField 上的有效参数。您需要在 on_delete 的 ForeignKey 模型中的每个 through 字段中使用 ChannelMembers 参数。
您可以通过以下示例了解如何在 Django Docs website 上实现
在您的情况下，它看起来像这样:

class Channel(models.Model):
    ...
    # Don't have the on_delete parameter on this field
    subscribers = models.ManyToManyField(User, through="ChannelMembers")

# Add on_delete to both the fields in this class instead
class ChannelMembers(models.Model):
    channel = models.ForeignKey(Channel, on_delete=models.CASCADE)
    subscriber = models.ForeignKey(User, on_delete=models.CASCADE)