Question

What is the best way to set a JSONField to have the default value of a new list in django?

在django中将JSONField设置为具有新列表的默认值的最佳方法是什么？

Context

There is a model where one of the fields is a list of items. In the case where there are no items set, the model should have an empty list.

有一个模型，其中一个字段是项目列表。在没有设置项目的情况下，模型应该有一个空列表。

Current solution

from django.models import Model

class MyModel(Model):
    the_list_field = JSONField(default=[])

Is this the best way to do it? Should it be switched to use list instead?

这是最好的方法吗？是否应该切换到使用列表？

Thanks!

谢谢！

1 个解决方案

#1

According to the Django documentation for JSONField you should indeed use default=list because using default=[] would create a mutable object that is shared between all instances of your field and could lead to some objects not having an empty list as a default.

根据JSONField的Django文档，您确实应该使用default = list，因为使用default = []会创建一个可变对象，该对象在您的字段的所有实例之间共享，并且可能导致某些对象没有空列表作为默认值。

Please note that this does not only apply for django.contrib.postgres.fields.JSONField but for all other kinds of objects and functions in Python in general.

请注意，这不仅适用于django.contrib.postgres.fields.JSONField，而且适用于Python中的所有其他类型的对象和函数。

Quote from the docs:

从文档引用：

If you give the field a default, ensure it’s a callable such as list (for an empty default) or a callable that returns a list (such as a function). Incorrectly using default=[] creates a mutable default that is shared between all instances of

如果为该字段指定默认值，请确保它是可调用的，例如list（对于空的默认值）或可调用的返回列表（例如函数）。错误地使用default = []会创建一个在所有实例之间共享的可变默认值

#1