Django Admin list_display添加列[相关ForeignKey的计数记录]

Question

我是Python和Django的新手.

我试图计算模型的外键项/记录,并将其显示为Admin list_display中的列.

所以我有一个模型"作者",作为模型"书"的外键.

这是models.py:

class Author(models.Model):

    name = models.CharField(
        max_length=100,
    )

    class Meta:
        ordering = ['-name ']
        verbose_name = _('Author')
        verbose_name_plural = _('Authors')

    def __str__(self):
        return self.author

    @models.permalink
    def get_absolute_url(self):
        return reverse('author_detail', kwargs={'pk': self.pk})

class Book(models.Model):
    author = models.ForeignKey(
        'Author',
        related_name='menu_items', 
        verbose_name=_('author'),
    )

    bookname= models.CharField(
        max_length=100,
    )

    publisher= models.CharField(
        max_length=100,
    )
    class Meta:
        ordering = ['-bookname']
        verbose_name = _('Book')
        verbose_name_plural = _('Books')

    def __str__(self):
        return self.bookname

    @models.permalink
    def get_absolute_url(self):
        return ('book_detail', [self.pk])

这是admin.py

from django.contrib import admin
from .models import Author, Book

class BookInline(admin.TabularInline):
    model = Book
    extra = 1

@admin.register(Author)
class LibraryAdmin(admin.ModelAdmin):
    def NumberOfBooks(self, obj):
        #I guess sth is wrong here when trying to count the book_set
        return obj.book_set.count()

    NumberOfBooks.short_description = "Books Count"
    list_display = ['bookname', 'publisher', 'NumberOfBooks']
    inlines = [BookInline]

我想计算每个作者写的书数量,并在管理页面的第二级显示如下:首页>作者>作者:

 Author | Books Count
Someone1  NumberOfBooks
Someone2  NumberOfBooks
Someone3  NumberOfBooks
Someone4  NumberOfBooks

但是我得到错误:

'Author' object has no attribute 'book_set'

1.我做obj.book_set.count()错了吗？ 我认为obj.book_set在同一个"作者"(obj)下会提到"书",听起来我误解了它,但我不确定如何实现我的意图.

2.相反,如果我想在"作者"中添加一个字段来自动计算与每个作者相关的"书籍"的数量,那么这应该是一个更好的方法,那么如何做呢？

Answer 1

应该有一个列表,其中包含错误页面上的所有可用字段,您应该找到一个名为的字段menu_items(这是您related_name在Book模型中添加的字段).

但这可能不是最好的选择.您应该能够像这样覆盖类get_queryset()上的方法LibraryAdmin(admin.ModelAdmin):

...
from django.db.models import Count
...

@admin.register(Loan)
class LibraryAdmin(admin.ModelAdmin):

    def get_queryset(self, request):
        qs = super(LibraryAdmin, self).get_queryset(request)
        return qs.annotate(books_count=Count('menu_items'))

    def books_count(self, inst):
        return inst.books_count

    list_display = ['bookname', 'publisher', 'books_count']
    inlines = [BookInline]

这种方式计数将由您的数据库完成.