Django ManyToManyField:'function'对象不可订阅

Question

因此,您意识到模型中的外键实际上应该是m2m,并且您已采用该实践来提供models.CASCADE作为外键的位置参数.所以你最终得到这个代码:

class Group(models.Model):
    members = models.ManyToManyField(Person, models.CASCADE)

你"修复"了一些其他的东西,突然结束了你试图做的所有事情的回溯尾巴:

File "/usr/local/lib/python3.5/site-packages/django/db/models/base.py", line 157, in __new__
    new_class.add_to_class(obj_name, obj)
File "/usr/local/lib/python3.5/site-packages/django/db/models/base.py", line 316, in add_to_class
    value.contribute_to_class(cls, name)
File "/usr/local/lib/python3.5/site-packages/django/db/models/fields/related.py", line 1516, in contribute_to_class
    elif self.remote_field.is_hidden():
File "/usr/local/lib/python3.5/site-packages/django/db/models/fields/reverse_related.py", line 144, in is_hidden
    return bool(self.related_name) and self.related_name[-1] == '+'
TypeError: 'function' object is not subscriptable

这是怎么回事？

Answer 1

ManyToManyField和ForeignKey的方法签名不相同.ManyToManyField第二个位置参数实际上是'related_name',这意味着您最终将models.CASCADE传递给related_name,如调试器中所示:

> /usr/local/lib/python3.5/site-packages/django/db/models/fields/related.py(1513)contribute_to_class()
-> if self.remote_field.symmetrical and (
(Pdb) p self.remote_field.related_name
<function CASCADE at 0x80645b400>

现在把它贴在你的显示器上,因为在3个月内你会再次使用它.