Django 查询 ManytoMany 字段

Question

我正在创建一个简单的 django 项目，它处理书籍和作者姓名的存储以及待读列表 (TBR) 的存储。 TBR table 连接到书籍 table 为多对多。

现在，我对如何查询特定 TBR 中的图书列表感到困惑。

我写的代码如下：

class BookManager(models.Manager):
    def is_read(self):
        return self.filter(read='y')

    def is_not_read(self):
        return self.filter(read='n')

class Genre(models.Model):
    name = models.CharField(max_length=200, help_text='Enter a book genre (e.g. Science Fiction)')

    def __str__(self):
        return self.name

class Author(models.Model):
    first_name = models.CharField(max_length=100, help_text="Enter first name of the author",default="Unknown")
    last_name = models.CharField(max_length=100, help_text="Enter last name of the author",default="Unknown")

    def __str__(self):
        return f'{self.first_name} {self.last_name}'

class Book(models.Model):

    YES = 'y'
    NO = 'n'

    DID_READ_CHOICES = [
        (YES,'Yes'),
        (NO,'No'),
    ]

    title = models.CharField(max_length=100)
    author = models.ForeignKey(
        Author,
        on_delete=models.SET_NULL, 
        null=True,
        related_name='author_books'
        )
    genre = models.ManyToManyField(Genre, help_text='Select a genre for this book')
    summary = models.TextField(max_length=1000, help_text='Enter a brief description of the book',blank=True,null=True)
    read = models.CharField(
        max_length=1,
        choices=DID_READ_CHOICES,
        default=NO,
        )

    objects = BookManager()

    class Meta:
        ordering = ['title']

    def __str__(self):
        return self.title

class TBR(models.Model):
    title = models.CharField(max_length=100)
    book = models.ManyToManyField(
        Book,
        related_name='in_tbr',
        )

    class Meta:
        ordering = ['title']

    def __str__(self):
        return self.title

我是 Django 的新手，我指的是 Django 文档，如有任何帮助，我们将不胜感激。

谢谢

编辑：我尝试了以下操作：

>>> to_be_read = TBR.objects.get(title='TBR1')
>>> for book in to_be_read.book:
...     book.title
...

但出现以下错误：

Traceback (most recent call last):
File "", line 1, in
TypeError: 'ManyRelatedManager' object is not iterable

Answer 1

你应该使用book.all()

试试这个

>>> to_be_read = TBR.objects.get(title='TBR1')
>>> for book in to_be_read.book.all():
...     book.title
...

Django 查询 ManytoMany 字段

Django Querying ManytoMany field

django

django-models

django-queryset