Django ModelForm组件使用方法详解

一、创建ModelForm

from django.forms import ModelForm
from appxx import models
from django.forms import widgets as wdt # 因为重名，所以起个别名
#定义一个类，比如BookForm，这个类要继承ModelForm，在这个类中再写一个原类Meta（规定写法，注意首字母是大写的）
#在这个原类中，有以下属性（部分）：
class BookForm(ModelForm):
  class Meta:
    model = models.Book # 对应的Model中的类
    fields = "__all__" # 字段，如果是__all__，就表示列出所有的字段，或者使用列表列出想要的字段
    exclude = None # 排除的字段
    # error_messages用法
    error_messages = {
      "title": {"required": "书名不能为空"},
      "price": {"required": "售价不能为空"},
    }
    # widgets用法，比如把输入用户名的input框给为Textarea
    widgets = {
      "name": wdt.Textarea(attrs={"class": "c1"}) # 还可以自定义属性
    }
    #labels，自定义在前端显示的名字
    labels= {
      "title": "书名",
      "price": "售价",
    }

然后在 url 对应的视图函数中实例化这个类，把这个对象传给前端：

def add_book(request):
  form = forms.BookForm()
  return render(request, "add_book.html", {"form": form})

然后在前端像Form组件那样渲染页面

二、添加数据

保存数据的时候，不用挨个取数据了，只需要 save 一下即可。

from django.shortcuts import render,redirect
from appxx import models
from appxx import forms

def add_book(request):
  if request.method == "POST":
    form = forms.BookForm(request.POST)
    if form.is_valid():
      form.save()
      return redirect("/book/")
  form = forms.BookForm()
  return render(request, "add_book.html", {"form": form})

三、编辑数据

如果不使用 ModelForm，编辑的时候得显示之前的数据，还得挨个取一遍值；如果使用 ModelForm，只需要加一个instance=obj（obj是要修改的数据库的一条数据的对象）就可以得到同样的效果。

保存的时候要注意，一定要注意有这个对象（instance=obj），否则不知道更新哪一个数据。

from django.shortcuts import render,redirect
from appxx import models
from appxx import forms

def edit_book(request, edit_book_id):
  edit_book= models.Book.objects.filter(id=edit_book_id).first()
  if request.method == "POST":
    form = forms.BookForm(request.POST, instance=edit_book)
    if form.is_valid():
      form.save()
      return redirect("/book/")
  form = forms.BookForm(instance=edit_book)
  return render(request, "edit_book.html", {"form": form})

总结： 从上边可以看到 ModelForm 用起来是非常方便的，比如增加修改之类的操作。但是也带来额外不好的地方，model和form之间耦合了。如果不耦合的话，form.save()方法也无法直接提交保存。 但是耦合的话使用场景通常局限用于小程序，写大程序就最好不用了。

四、完整示例代码

项目结构

urls.py

from django.conf.urls import url
from django.contrib import admin
from appxx import views

urlpatterns = [
  url(r'^admin/', admin.site.urls),
  url(r"^book/$", views.book),
  url(r"^book/add/", views.add_book),
  url(r"^book/edit/(\d+)/", views.edit_book),
]

views.py

from django.shortcuts import render,redirect
from appxx import models
from appxx import forms

def book(request):
  book_list = models.Book.objects.all()
  return render(request, "book.html", {"book_list": book_list})

def add_book(request):
  if request.method == "POST":
    form = forms.BookForm(request.POST)
    if form.is_valid():
      form.save()
      return redirect("/book/")
  form = forms.BookForm()
  return render(request, "add_book.html", {"form": form})

def edit_book(request, edit_book_id):
  edit_book= models.Book.objects.filter(id=edit_book_id).first()
  if request.method == "POST":
    form = forms.BookForm(request.POST, instance=edit_book)
    if form.is_valid():
      form.save()
      return redirect("/book/")
  form = forms.BookForm(instance=edit_book)
  return render(request, "edit_book.html", {"form": form})

models.py

from django.db import models

class Book(models.Model):
  id = models.AutoField(primary_key=True)
  title = models.CharField(max_length=32)
  price = models.DecimalField(max_digits=5, decimal_places=2)
  publish_date = models.DateField()
  publisher = models.ForeignKey(to="Publisher")
  authors = models.ManyToManyField(to="Author")

  def __str__(self):
    return self.title

class Publisher(models.Model):
  id = models.AutoField(primary_key=True)
  name = models.CharField(max_length=32)

  def __str__(self):
    return self.name

class Author(models.Model):
  id = models.AutoField(primary_key=True)
  name = models.CharField(max_length=32)

  def __str__(self):
    return self.name

forms.py

from django.forms import ModelForm
from appxx import models
from django.forms import widgets as wdt

class BookForm(ModelForm):
  class Meta:
    model = models.Book
    fields = "__all__"
    labels = {
      "title": "书名",
      "price": "售价",
      "publish_date": "出版日期",
      "publisher": "出版社",
      "authors": "作者"
    }
    widgets = {
      "title": wdt.TextInput(attrs={"class": "form-control"}),
      "price": wdt.TextInput(attrs={"class": "form-control"}),
      "publish_date": wdt.TextInput(attrs={"class": "form-control", "type": "date"}),
      "publisher": wdt.Select(attrs={"class": "form-control"}),
      "authors": wdt.SelectMultiple(attrs={"class": "form-control"}),

    }
    error_messages = {
      "title": {"required": "书名不能为空"},
      "price": {"required": "售价不能为空"},
      "publish_date": {"required": "出版日期不能为空"},
      "publisher": {"required": "出版社不能为空"},
      "authors": {"required": "作者不能为空"},
    }

book.html

<!DOCTYPE html>
<html lang="zh-cn">
<head>
  <meta charset="UTF-8">
  <title>展示书籍</title>
  <link rel="stylesheet" href="/static/bootstrap/css/bootstrap.min.css" rel="external nofollow" rel="external nofollow" >
</head>
<body>
<div class="container">
  <div class="row">
    <div class="col-md-6 col-md-offset-3">
      <span><a class="btn btn-primary" href="/book/add/" rel="external nofollow" >添加</a></span>
      <table class="table table-striped table-bordered">
        <thead>
        <tr>
          <th>序号</th>
          <th>书名</th>
          <th>售价</th>
          <th>出版日期</th>
          <th>出版社</th>
          <th>作者</th>
          <th>操作</th>
        </tr>
        </thead>
        <tbody>
        {% for book in book_list %}
          <tr>
            <td>{{ forloop.counter }}</td>
            <td>{{ book.title }}</td>
            <td>{{ book.price }}</td>
            <td>{{ book.publish_date }}</td>
            <td>{{ book.publisher.name }}</td>
            <td>
              {% for author in book.authors.all %}
                {{ author.name }}
              {% endfor %}
            </td>
            <td>
              <span><a class="btn btn-warning" href="/book/edit/{{ book.pk }}/" rel="external nofollow" >编辑</a></span>
              <span><a class="btn btn-danger" href="">删除</a></span>
            </td>
          </tr>
        {% endfor %}
        </tbody>
      </table>
    </div>
  </div>
</div>
</body>
</html>

add_book.html和edit_book.html（两个页面代码一样）

<!DOCTYPE html>
<html lang="zh-cn">
<head>
  <meta charset="UTF-8">
  <title>添加书籍</title>
  <link rel="stylesheet" href="/static/bootstrap/css/bootstrap.min.css" rel="external nofollow" rel="external nofollow" >
  <style>
    .panel-title {
      font-weight: bolder;
    }

    .panel {
      margin-top: 30px;
    }
  </style>
</head>
<body>
<div class="container">
  <div class="row">
    {# panel开始 #}
    <div class="panel panel-danger col-sm-6 col-md-6 col-sm-offset-3 col-md-offset-3">
      <div class="panel-heading">
        <h3 class="panel-title">添加书籍</h3>
      </div>
      {# panel-body开始 #}
      <div class="panel-body">
        {# form开始 #}
        <form class="form-horizontal" action="" method="post" novalidate>
          {% csrf_token %}
          <div class="form-group">
            <label class="col-md-2 control-label"
                for="{{ form.title.id_for_label }}">{{ form.title.label }}</label>
            <div class="col-md-10">
              {{ form.title }}
            </div>
          </div>
          <div class="form-group">
            <label class="col-md-2 control-label"
                for="{{ form.price.id_for_label }}">{{ form.price.label }}</label>
            <div class="col-md-10">
              {{ form.price }}
            </div>
          </div>
          <div class="form-group">
            <label class="col-md-2 control-label"
                for="{{ form.publish_date.id_for_label }}">{{ form.publish_date.label }}</label>
            <div class="col-md-10">
              {{ form.publish_date }}
            </div>
          </div>
          <div class="form-group">
            <label class="col-md-2 control-label"
                for="{{ form.publisher.id_for_label }}">{{ form.publisher.label }}</label>
            <div class="col-md-10">
              {{ form.publisher }}
            </div>
          </div>
          <div class="form-group">
            <label class="col-md-2 control-label"
                for="{{ form.authors.id_for_label }}">{{ form.authors.label }}</label>
            <div class="col-md-10">
              {{ form.authors }}
            </div>
          </div>
          <div class="form-group">
            <div class="col-md-offset-2 col-md-10">
              <button type="submit" class="btn btn-success">提交</button>
              <a class="btn btn-warning pull-right" href="/book/" rel="external nofollow" >取消</a>
            </div>
          </div>
        </form>
        {# form结束 #}
      </div>
      {# panel-body结束 #}
    </div>
    {# panel结束 #}
  </div>
</div>
</body>
</html>

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