无法在 Django 中获取关系属性，多对多关系

Question

models.py:

class Author(models.Model):
    name = models.CharField(max_length=100)

    def __str__(self):
        return self.name

class Book(models.Model):
    title = models.CharField(max_length=100)
    author = models.ManyToManyField(Author)
   
    def __str__(self):
        return self.title

我可以通过 author 关系过滤 books：

>>> Book.objects.filter(author__name__contains="Fyodor")
<QuerySet [<Book: Crime and Punishment>, <Book: The Brothers Karamazov>]>

但是，我无法获得 本书的作者：

>>> all_books = Book.objects.all()
>>> all_books[0].author
<django.db.models.fields.related_descriptors.create_forward_many_to_many_manager.<locals>.ManyRelatedManager object at 0x7fdf068a2b20>
>>> all_books[0].author.name
>>>

有什么建议吗？

Answer 1

书籍和作者之间存在 ManyToMany 关系，因此每本书都会有很多作者。因此 book.author 给你一个作者查询集。

因此你需要做这样的事情：

# get a single book:
book = Book.objects.get(id=<the-book-id>)

# get all the authors of a book:
authors = book.author.all()

# get the first author of the book:
first_author = authors.first()
name = first_author.name

无法在 Django 中获取关系属性，多对多关系

Unable to get relation attribute in Django, many-to-many relationship

django

django-models