Django 2 to 3 upgrade throws error: "on_delete must be callable"

Question

在从 Django 2 升级到 3.2 时，在运行我的服务器上，我突然收到以下错误：

TypeError: on_delete must be callable.

有问题的模型字段是这个：

game_played = models.ForeignKey(Game, "Game Played", help_text="Game Played", null=True, blank=False)

如您所见，on_delete 未在此字段上调用。恢复到 Django 2 修复了这个问题，因为它不再 returns 错误。我试图将 on_delete 添加到该字段，结果出现此错误：

TypeError: __init__() got multiple values for argument 'on_delete'

我查看了 Django 3 文档，但找不到任何与 on_delete 相关的更改会影响到此。关于 on_delete 问题，我所能找到的只是有时人们将 models.CASCADE 放在引号中而不是使其可调用，但这不是这里的问题。

我该如何解决这个问题？

Answer 1

你应该为 on_delete 提供一个不能放弃的论据。此外，ForeignKey 的 __init__ 的第二个参数不是您假设的 verbose_name，而是 on_delete，因此您应该将 verbose_name 作为kwarg 如果你需要：

# pass `verbose_name` as kwarg
# pass `on_delete` it cannot be foregone
game_played = models.ForeignKey(Game, on_delete=models.CASCADE, verbose_name="Game Played", help_text="Game Played", null=True, blank=False)

Note: Don't know why you don't get this error in Django 2, looking at the source code the second argument is also on_delete in that version, should have given you some error at least at the time of deletion if not at instantiation.

Answer 2

只需添加 on_delete，我认为您不需要“玩过游戏”，因此它看起来像这样：

game_played = models.ForeignKey(Game, help_text="Game Played", null=True, blank=False, on_delete = models.CASCADE)

然后在您的终端中进行迁移和迁移

Django 2 to 3 upgrade throws error: "on_delete must be callable"

Django 2 to 3 upgrade throws error: "on_delete must be callable"

python

python-3.x

django

django-3.0