Django ModelForm组件

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，具体点击这里

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">
</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/">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 }}/">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">
    <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/">取消</a>
                        </div>
                    </div>
                </form>
                {# form结束 #}
            </div>
            {# panel-body结束 #}
        </div>
        {# panel结束 #}
    </div>
</div>
</body>
</html>