下拉框 -------> 初始化数据

在Web应用程序中开发编写功能时，时常用到获取数据库中的数据并将值初始化在HTML中的标签上。

1、Form

from django.forms import Form
from django.forms import widgets
from django.forms import fields
from django.core.validators import RegexValidator
 
class MyForm(Form):
    user = fields.CharField()
 
    city = fields.ChoiceField(
        choices=((1, '上海'), (2, '北京'),),
        widget=widgets.Select
    )

2、views

from django.shortcuts import render, redirect
from .forms import MyForm
 
def index(request):
    if request.method == "GET":
        values = {'user': 'root', 'city': 2}
        obj = MyForm(values)
 
        return render(request, 'index.html', {'form': obj})
    elif request.method == "POST":
        return redirect('http://www.google.com')
    else:
        return redirect('http://www.google.com')

3、HTML

<form method="POST" enctype="multipart/form-data">
    {% csrf_token %}
    <p>{{ form.user }} {{ form.user.errors }}</p>
    <p>{{ form.city }} {{ form.city.errors }}</p>
 
    <input type="submit"/>
</form>

　　initial

在使用选择标签时，需要注意choices的选项可以从数据库中获取，但是由于是静态字段 ***获取的值无法实时更新***，那么需要自定义构造方法从而达到此目的。

方法一：(推荐)
 
from django.forms import Form
from django.forms import widgets
from django.forms import fields
from django.core.validators import RegexValidator
 
class MyForm(Form):
 
    user = fields.ChoiceField(
        # choices=((1, '上海'), (2, '北京'),),
        initial=2,
        widget=widgets.Select
    )
 
    def __init__(self, *args, **kwargs):
　　　　　　# 拷贝所有的静态字段，赋值给self.fields
        super(MyForm,self).__init__(*args, **kwargs)
        self.fields['user'].widget.choices = models.Classes.objects.all().value_list('id','caption')

　　

方式二：
 
使用django提供的ModelChoiceField和ModelMultipleChoiceField字段来实现
 
from django import forms
from django.forms import fields
from django.forms import widgets
from django.forms import models as form_model
from django.core.exceptions import ValidationError
from django.core.validators import RegexValidator
 
class FInfo(forms.Form):
    authors = form_model.ModelMultipleChoiceField(queryset=models.NNewType.objects.all())
    # authors = form_model.ModelChoiceField(queryset=models.NNewType.objects.all())

　　

五、自定义配置

1、在settings中：

2、导入settings

from django.conf import settings

　　 3、使用

六、多对多修改两种方式（用Form）

def editteacher(request,nid):
    obj = models.UserInfo.objects.filter(id=nid, ut_id=1).first()
    # print(obj.username)
    if not obj:
        return redirect("/teacherindex/")
    if request.method=="GET":
        print([obj.id for obj in obj.teacher_classes.all()])  #[2]  拿到select框的id是为了要做默认显示的
        form = TeacherForm(initial={"username":obj.username,"password":obj.password,"email":obj.email,"teacher_classes":[obj.id for obj in obj.teacher_classes.all()]}) #就让显示一个input框，并且带有原来哪一行的内容
        return render(request, "editteacher.html", {"form":form})
    else:
        form = TeacherForm(data=request.POST)
        if form.is_valid():#开始校验,注意这要加括号
            cls_list = form.cleaned_data.pop("teacher_classes")
            print(cls_list)
            models.UserInfo.objects.filter(id=nid).update(**form.cleaned_data)
            obj.teacher_classes.set(cls_list)   #更新第三张表
            return redirect("/teacherindex/")
        else:
            return render(request, "editteacher.html", {"form":form})

　　

七、多对多添加（用Form）

def addteacher(request):
    if request.method=="GET":
        form = TeacherForm()  #只是让显示一个input框
        return render(request, "addteacher.html", {"form":form})
    else:
        form = TeacherForm(data=request.POST)
        # print(form)  #<QuerySet [<UserInfo: UserInfo object>, <UserInfo: UserInfo object>, <UserInfo: UserInfo object>]>
        if form.is_valid():# 开始验证
            # print('执行成功',form.cleaned_data)          # 所有匹配成功，字典
            # # {'username': 'ghf', 'password': '435', 'email': 'fddfg@qq.com', 'teacher_classes': ['4']}
            cls_list = form.cleaned_data.pop("teacher_classes")
            print("============id",cls_list)
            form.cleaned_data['ut_id'] = 1
            #创建新老师的对象
            teacher_obj = models.UserInfo.objects.create(**form.cleaned_data)
            #创建新老师和班级的关系
            teacher_obj.teacher_classes.add(*cls_list)  #以前添加的是对象，现在也可以吧id添加进去
            return redirect("/teacherindex/")
        else:
            # print("=====?",form.errors,type(form.errors))#返回失败的结果
            # print(form.errors["username"][0])   #拿到返回失败的结果，渲染到页面
            return render(request, "addteacher.html", {"form":form})