Django ModelForm显示外键的模型字段，而不是对象id

# models.py
from django.db import models

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

class Book(models.Model):
    title = models.CharField(max_length=100)
    author = models.ForeignKey(Author, on_delete=models.CASCADE)

# forms.py
from django import forms
from .models import Book

class BookForm(forms.ModelForm):
    class Meta:
        model = Book
        fields = ['title', 'author']  # 包含外键字段author

# views.py
from django.shortcuts import render
from .forms import BookForm

def create_book(request):
    if request.method == 'POST':
        form = BookForm(request.POST)
        if form.is_valid():
            form.save()
            return redirect('book_list')
    else:
        form = BookForm()
    return render(request, 'create_book.html', {'form': form})

# create_book.html
<form method="post">
  {% csrf_token %}
  {{ form.as_p }}
  <button type="submit">保存</button>
</form>