How to update manytomany field in Django?

Question

Here\'s an example:

If I have these classes

class Author(models.Model):
    name = models.CharField(max_length=45)

class Book(models.Model):
    nam         


        

Answer 1

With the auto-generated through table, you can do a two-step insert and delete, which is nice for readability.

george = Author.objects.get(name='George')
georfe = Author.objects.get(name='Georfe')

book.authors.add(george)
book.authors.remove(georfe)
assert george in book.authors

If you have an explicitly defined through table (authors = models.ManyToManyField(Author, through=BookAuthors) then you can change the relationship explicitly on BookAuthor. A little known fact is that this Model already exists, it is generated by django automatically. Usually you should only create an explicit through model if you have extra data you wish to store (for instance the chapters a particular author wrote, in a multi-author book).

# This line is only needed without a custom through model.
BookAuthor = Book.authors.through
book_author = BookAuthor.objects.get(author=georfe, book=great_american_novel)
book_author.author = george
book_author.save()
assert george in book.authors