使用变量中的字段名称更新 django 中的多对多字段

发布于 2024-12-19 06:48:02 字数 729 浏览 4 评论 0原文

当字段名称存储在变量中时，我希望能够更新模型上的多对多字段。这对于普通字段（构造函数中带有 kwargs）甚至外键来说相对容易，但对于多对多字段则不然。情况是这样的：

class Book(models.Model):
    title = models.CharField(max_length=30)
    authors = models.ManyToManyField(Author)

field_name = 'title'
new = Book(**{field_name:'My Book'}) # This sets title to mybook
new.save()
my_authors = Author.objects.filter(name='Ben') # Get some authors
field_name = 'authors' 
new.XXXXXX = my_authors # Add them

我要问的是如何做 XXXXXX 位！它不像其他字段一样在 kwargs 中被接受，因为您首先需要一个主键，并且在保存它之前不会发生这种情况。有什么想法吗？非常感谢任何帮助！这一定是可能的 - django 管理员必须以某种方式做到这一点，但我找不到在哪里。

*编辑 - 我理想地寻找一个不使用 __getattribute 或 __setattr 的解决方案 - 尽管它们确实有效，但并不理想。另外，在执行此操作时我无法以任何方式更改模型，那是其他人的代码。谢谢！

谢谢你们。本

原文

I want to be able to update a many-to-many field on a model, when the name of the field is stored in a variable. This is relatively easy for a normal field (with kwargs in the constructor), or even a foreign key, but not so for a many-to-many field. Here's the situation:

class Book(models.Model):
    title = models.CharField(max_length=30)
    authors = models.ManyToManyField(Author)

field_name = 'title'
new = Book(**{field_name:'My Book'}) # This sets title to mybook
new.save()
my_authors = Author.objects.filter(name='Ben') # Get some authors
field_name = 'authors' 
new.XXXXXX = my_authors # Add them

How to do the XXXXXX bit is what I'm asking! It isn't accepted in the kwargs like other fields, as you need a primary key first and that can't happen until it's been saved. Any ideas? Any help very greatly appreciated! It must be possible - the django admin must do it some how but I can't find where.

*Edit - I'm ideally looking for a solution that doesn't use __getattribute or __setattr - though they do work, they're not ideal. Also, I can't alter the model in any way when doing this, that's somebody else's code. Thanks!

Thanks guys.
Ben

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じее 2024-12-26 06:48:02

阅读您的答案，我认为这就是您正在寻找的：

relation_name = 'authors'
new.__getattribute__(relation_name) = my_authors

没有参数化关系名称 django n:m doc 说：

new.authors = my_authors

Reading your answer, I think that this is you are looking for:

relation_name = 'authors'
new.__getattribute__(relation_name) = my_authors

With out parametrize relation name django n:m doc say:

new.authors = my_authors

回复收藏 0 原文

那请放手 2024-12-26 06:48:02

这假设作者不是被创建的，而是被添加到书籍的 M2M 字段中的。

my_authors = Author.objects.filter(name='Ben') # Get some authors

# This will append all authors from my_authors to the M2M field.
for a in my_authors:
    new.authors.add(a)

这是您要找的吗？

This assumes that the authors are not being created, but being added to the M2M field for the book.

my_authors = Author.objects.filter(name='Ben') # Get some authors

# This will append all authors from my_authors to the M2M field.
for a in my_authors:
    new.authors.add(a)

Is this what you are looking for?

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