在 Django 中，使用 ModelForm 来处理表单与模型之间的交互是非常方便的。当你需要在表单中传递一个实例（即一个数据库模型的对象），有几种方法可以实现这一点。以下是几种不同的方式以及它们的步骤流程和示例代码。
假设我们有一个名为 Book 的模型，它具有 title 和 author 两个字段。
# models.py
from django.db import models
class Book(models.Model):
title = models.CharField(max_length=100)
author = models.CharField(max_length=100)
def __str__(self):
return self.title
步骤流程：
ModelForm 实例，将实例对象传递给它。ModelForm 实例传递给模板渲染。# views.py
from django.shortcuts import render
from .models import Book
from .forms import BookForm
def edit_book(request, book_id):
book_instance = Book.objects.get(pk=book_id)
if request.method == 'POST':
form = BookForm(request.POST, instance=book_instance)
if form.is_valid():
form.save()
# 处理表单提交后的逻辑
else:
form = BookForm(instance=book_instance)
return render(request, 'edit_book.html', {'form': form})
<!-- edit_book.html -->
<form method="post">
{% csrf_token %}
{{ form.as_p }}
<button type="submit">Save</button>
</form>
步骤流程：
UpdateView 的类视图。model 属性为你的模型类，设置 form_class 属性为你的 ModelForm 类。get_object 方法，返回要传递的实例对象。# views.py
from django.urls import reverse_lazy
from django.views.generic.edit import UpdateView
from .models import Book
from .forms import BookForm
class BookUpdateView(UpdateView):
model = Book
form_class = BookForm
template_name = 'edit_book.html'
success_url = reverse_lazy('book_list') # Redirect URL after successful form submission
def get_object(self, queryset=None):
book_id = self.kwargs.get('book_id')
return Book.objects.get(pk=book_id)
<!-- edit_book.html -->
<form method="post">
{% csrf_token %}
{{ form.as_p }}
<button type="submit">Save</button>
</form>
步骤流程：
ModelForm 的自定义表单类。__init__ 方法中，接收并处理传递的实例对象。# forms.py
from django import forms
from .models import Book
class BookForm(forms.ModelForm):
class Meta:
model = Book
fields = ['title', 'author']
def __init__(self, *args, **kwargs):
instance = kwargs.get('instance')
super().__init__(*args, **kwargs)
if instance:
self.fields['title'].initial = instance.title
self.fields['author'].initial = instance.author
# views.py
from django.shortcuts import render
from .models import Book
from .forms import BookForm
def edit_book(request, book_id):
book_instance = Book.objects.get(pk=book_id)
if request.method == 'POST':
form = BookForm(request.POST, instance=book_instance)
if form.is_valid():
form.save()
# 处理表单提交后的逻辑
else:
form = BookForm(instance=book_instance)
return render(request, 'edit_book.html', {'form': form})
<!-- edit_book.html -->
<form method="post">
{% csrf_token %}
{{ form.as_p }}
<button type="submit">Save</button>
</form>
无论使用哪种方式，都可以在表单中传递一个数据库模型的实例对象，使得编辑和更新操作更加方便。
