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分享两种方法解决Form表单数据无法动态刷新的方法

时间:2021-07-01 10:21:17 帮助过:17人阅读

一、无法动态更新数据的实例

1. 如下,数据库中创建了班级表和教师表,两张表的对应关系为“多对多”

 1 from django.db import models 2  3  4 class Classes(models.Model): 5     title = models.CharField(max_length=32) 6  7  8 class Teacher(models.Model): 9     name = models.CharField(max_length=32)10     t2c = models.ManyToManyField(Classes)
models.py

2. views的功能有查看、添加、编辑班级或教师表

 1 from django.shortcuts import render, redirect 2 from school import models 3 from django.forms import Form, fields, widgets 4  5  6 #班级表单验证规则 7 class ClsForm(Form): 8     title = fields.RegexField('老男孩', error_messages={'invalid': '请以 老男孩 开头'}) 9 10 11 #教师表单验证规则12 class TchForm(Form):13     name = fields.CharField(max_length=16, min_length=2, widget=widgets.TextInput(attrs={'class': 'form-control'}))14     t2c = fields.MultipleChoiceField(15         choices=models.Classes.objects.values_list('id', 'title'),16         widget=widgets.SelectMultiple(attrs={'class': 'form-control'})17     )18 19 20 #查看班级列表21 def classes(request):22     cls_list = models.Classes.objects.all()23     return render(request, 'classes.html', {'cls_list': cls_list})24 25 26 #查看教师列表27 def teachers(request):28     tch_list = models.Teacher.objects.all()29     return render(request, 'teachers.html', {'tch_list': tch_list})30 31 32 #添加班级33 def add_cls(request):34     if request.method == 'GET':35         obj = ClsForm()36         return render(request, 'add_classes.html', {'obj': obj})37     else:38         obj = ClsForm(request.POST)39         if obj.is_valid():40             models.Classes.objects.create(**obj.cleaned_data)41             return redirect('/school/classes/')42         return render(request, 'add_classes.html', {'obj': obj})43 44 45 #添加教师46 def add_tch(request):47     if request.method == 'GET':48         obj = TchForm()49         return render(request, 'add_teacher.html', {'obj': obj})50     else:51         obj = TchForm(request.POST)52         if obj.is_valid():53             tc = obj.cleaned_data.pop('t2c')    # 获取教师任课班级id54             tch_obj = models.Teacher.objects.create(name=obj.cleaned_data['name'])  # 添加新教师姓名55             tch_obj.t2c.add(*tc)    # 添加新教师任课班级56             return redirect('/school/teachers/')57         return render(request, 'add_teacher.html', {'obj': obj})58 59 60 #编辑班级61 def edit_cls(request, nid):62     if request.method == 'GET':63         cls = models.Classes.objects.filter(id=nid).first()64         obj = ClsForm(initial={'title': cls.title})65         return render(request, 'edit_classes.html', {'nid': nid, 'obj': obj})66     else:67         obj = ClsForm(request.POST)68         if obj.is_valid():69             models.Classes.objects.filter(id=nid).update(**obj.cleaned_data)70             return redirect('/school/classes/')71         return render(request, 'edit_classes.html', {'nid': nid, 'obj': obj})72 73 74 #编辑教师75 def edit_tch(request, nid):76     if request.method == 'GET':77         tch = models.Teacher.objects.filter(id=nid).first()78         v = tch.t2c.values_list('id')   # 获取该教师任课班级的id79         cls_ids = list(zip(*v))[0] if list(zip(*v)) else []     # 格式化为列表类型80         obj = TchForm(initial={'name': tch.name, 't2c': cls_ids})81         return render(request, 'edit_teacher.html', {'nid': nid, 'obj': obj})82     else:83         obj = TchForm(request.POST)84         if obj.is_valid():85             tc = obj.cleaned_data.pop('t2c')    # 获取修改后的任课班级id86             # models.Teacher.objects.filter(id=nid).update(name=obj.cleaned_data['name'])     # 更新教师姓名方法187             tch_obj = models.Teacher.objects.filter(id=nid).first()88             tch_obj.name = obj.cleaned_data['name']     # 更新教师姓名方法289             tch_obj.save()90             tch_obj.t2c.set(tc)91             return redirect('/school/teachers/')92         return render(request, 'edit_teacher.html', {'nid': nid, 'obj': obj})
views.py

3. html文件

classe:

 1 <!DOCTYPE html> 2 <html lang="en"> 3 <head> 4     <meta charset="UTF-8"> 5     <title>班级列表</title> 6     <link rel="stylesheet" href="/static/plugins/bootstrap-3.3.7-dist/css/bootstrap.css?1.1.11"> 7 </head> 8 <body> 9 <div style="width: 700px; margin: 30px auto">10     <a class="btn btn-default" href="/school/add_cls/" style="margin-bottom: 10px">添加班级</a>11         <table class="table table-hover" border="1" cellspacing="0">12             <thead>13             <tr>14                 <th>ID</th>15                 <th>班级</th>16                 <th>操作</th>17             </tr>18             </thead>19             <tbody>20                 {% for item in cls_list %}21                     <tr>22                         <td>{{ item.id }}</td>23                         <td>{{ item.title }}</td>24                         <td><a href="/school/edit_cls/{{ item.id }}">编辑</a></td>25                     </tr>26                 {% endfor %}27             </tbody>28         </table>29 </div>30 </body>31 </html>
classes.html
 1 <!DOCTYPE html> 2 <html lang="en"> 3 <head> 4     <meta charset="UTF-8"> 5     <title>添加班级</title> 6 </head> 7 <body> 8 <h1>添加班级</h1> 9 <form action="/school/add_cls/" method="post">10     {% csrf_token %}11     <p>12         {{ obj.title }} {{ obj.errors.title.0 }}13     </p>14     <input type="submit" value="提交">15 </form>16 </body>17 </html>
add_classes.html
 1 <!DOCTYPE html> 2 <html lang="en"> 3 <head> 4     <meta charset="UTF-8"> 5     <title>编辑班级</title> 6 </head> 7 <body> 8 <h1>编辑班级</h1> 9 <form action="/school/edit_cls/{{ nid }}" method="post">10     {% csrf_token %}11     <p>12         {{ obj.title }} {{ obj.errors.title.0 }}13     </p>14     <input type="submit" value="提交">15 </form>16 </body>17 </html>
edit_classes.html

teachers:

 1 <!DOCTYPE html> 2 <html lang="en"> 3 <head> 4     <meta charset="UTF-8"> 5     <title>教师列表</title> 6     <link rel="stylesheet" href="/static/plugins/bootstrap-3.3.7-dist/css/bootstrap.css?1.1.11"> 7 </head> 8 <body> 9 <div style="width: 700px; margin: 30px auto">10     <a class="btn btn-default" href="/school/add_tch/" style="margin-bottom: 10px">添加教师</a>11         <table class="table table-hover" border="1" cellspacing="0">12             <thead>13             <tr>14                 <th>ID</th>15                 <th>姓名</th>16                 <th>任教班级</th>17                 <th>操作</th>18             </tr>19             </thead>20             <tbody>21                 {% for item in tch_list %}22                     <tr>23                         <td>{{ item.id }}</td>24                         <td>{{ item.name }}</td>25                         <td>26                             {% for row in item.t2c.all %}27                                 <span style="border: solid gray 1px">{{ row.title }}</span>28                             {% endfor %}29                         </td>30                         <td><a href="/school/edit_tch/{{ item.id }}">编辑</a></td>31                     </tr>32                 {% endfor %}33             </tbody>34         </table>35 </div>36 </body>37 </html>
teachers.html
 1 <!DOCTYPE html> 2 <html lang="en"> 3 <head> 4     <meta charset="UTF-8"> 5     <title>添加教师</title> 6     <link rel="stylesheet" href="/static/plugins/bootstrap-3.3.7-dist/css/bootstrap.css?1.1.11"> 7 </head> 8 <body> 9 <div style="width: 500px; margin: 20px auto">10 <h3 style="width: 100px; margin: 10px auto">添加教师</h3>11     <form class="form-horizontal" action="/school/add_tch/" method="post">12         {% csrf_token %}13   <div class="form-group">14     <label class="col-sm-2 control-label">姓名</label>15     <div class="col-sm-10">16       {{ obj.name }} {{ obj.errors.name.0 }}17     </div>18   </div>19   <div class="form-group">20     <label class="col-sm-2 control-label">班级</label>21     <div class="col-sm-10">22             {{ obj.t2c }} {{ obj.errors.t2c.0 }}23     </div>24   </div>25   <div class="form-group">26     <div class="col-sm-offset-2 col-sm-10">27       <input type="submit" class="btn btn-default" value="提交"></input>28     </div>29   </div>30 </form>31 </div>32 </body>33 </html>
add_teacher.html
 1 <!DOCTYPE html> 2 <html lang="en"> 3 <head> 4     <meta charset="UTF-8"> 5     <title>编辑教师</title> 6     <link rel="stylesheet" href="/static/plugins/bootstrap-3.3.7-dist/css/bootstrap.css?1.1.11"> 7 </head> 8 <body> 9 <div style="width: 500px; margin: 20px auto">10 <h3 style="width: 100px; margin: 10px auto">编辑教师</h3>11     <form class="form-horizontal" action="/school/edit_tch/{{ nid }}" method="post">12         {% csrf_token %}13   <div class="form-group">14     <label class="col-sm-2 control-label">姓名</label>15     <div class="col-sm-10">16       {{ obj.name }} {{ obj.errors.name.0 }}17     </div>18   </div>19 20   <div class="form-group">21     <label class="col-sm-2 control-label">班级</label>22     <div class="col-sm-10">23             {{ obj.t2c }} {{ obj.errors.t2c.0 }}24     </div>25   </div>26   <div class="form-group">27     <div class="col-sm-offset-2 col-sm-10">28       <input type="submit" class="btn btn-default" value="提交"></input>29     </div>30   </div>31 </form>32 </div>33 </body>34 </html>
edit_teacher.html

4. 数据不能同步

在班级表中新增一条记录

在教师表中新添加一名教师,发现无法获取上一步新增记录

5. 原因分析

在添加教师时,请求方式为GET,html标签由Form组件自动生成,其中的数据也是由Form组件提供

而TchForm作为一个类,在project运行起来后,其中的name和t2c字段都是类的变量,其只执行一次,就将数据保存在内存中,无论之后生成多少个TchForm对象,其中的字段的值都不变。

所以会出现教师表中的班级多选列表无法动态更新。

二、解决上述bug的方法

每次更新数据库后重启project,让Form类重新初始化,能够让数据更新,但这显然是不切实际的。

知道了bug的根源,我们可以尝试让每次生成TchForm对象时就更新数据:

方法一

1. 利用 __init__将数据库操作放入对象变量中

 1 #教师表单验证规则 2 class TchForm(Form): 3     name = fields.CharField(max_length=16, min_length=2, widget=widgets.TextInput(attrs={'class': 'form-control'})) 4     t2c = fields.MultipleChoiceField( 5         # choices=models.Classes.objects.values_list('id', 'title'), 6         widget=widgets.SelectMultiple(attrs={'class': 'form-control'}) 7     ) 8  9     def __init__(self, *args, **kwargs):    # 自定义__init__10         super(TchForm, self).__init__(*args, **kwargs)  # 调用父类的__init__11         self.fields['t2c'].choices = models.Classes.objects.values_list('id', 'title')   # 为字段t2c的choices赋值
修改TchForm类

2. 验证

在班级表中新增一条记录

再在教师表中添加

方法二

1. 利用django.forms.models模块中的queryset连接数据库

 1 #教师表单验证规则 2 from django.forms import models as form_models  # 导入django.forms.models 3 class TchForm(Form): 4     name = fields.CharField(max_length=16, min_length=2, widget=widgets.TextInput(attrs={'class': 'form-control'})) 5     #重新定义字段 6     t2c = form_models.ModelMultipleChoiceField( 7         # choices=models.Classes.objects.values_list('id', 'title'), 8         queryset=models.Classes.objects.all(),  # 利用queryset连接数据库,只能连接object类型 9         widget=widgets.SelectMultiple(attrs={'class': 'form-control'})10     )
修改TchForm类

2. 验证

由于TchForm类中,queryset只能连接object类型,所以,需要设置models.py中的Classes类的返回值。

1 class Classes(models.Model):2     title = models.CharField(max_length=32)3 4     def __str__(self):5         return self.title
设置models.py中的Classes类的返回值

在班级表中新增一条记录

再在教师表中添加

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