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
2
3
4
5
6
|
from django.db import models
class Classes(models.Model):
title = models.CharField(max_length=32)
class Teacher(models.Model):
name = models.CharField(max_length=32)
t2c = models.ManyToManyField(Classes)
|
2. views的功能有查看、添加、编辑班级或教师表
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
|
from django.shortcuts import render, redirect
from school import models
from django.forms import Form, fields, widgets
#班级表单验证规则
class ClsForm(Form):
title = fields.RegexField('老男孩', error_messages={'invalid': '请以 老男孩 开头'})
#教师表单验证规则
class TchForm(Form):
name = fields.CharField(max_length=16, min_length=2, widget=widgets.TextInput(attrs={'class': 'form-control'}))
t2c = fields.MultipleChoiceField(
choices=models.Classes.objects.values_list('id', 'title'),
widget=widgets.SelectMultiple(attrs={'class': 'form-control'})
)
#查看班级列表
def classes(request):
cls_list = models.Classes.objects.all()
return render(request, 'classes.html', {'cls_list': cls_list})
#查看教师列表
def teachers(request):
tch_list = models.Teacher.objects.all()
return render(request, 'teachers.html', {'tch_list': tch_list})
#添加班级
def add_cls(request):
if request.method == 'GET':
obj = ClsForm()
return render(request, 'add_classes.html', {'obj': obj})
else:
obj = ClsForm(request.POST)
if obj.is_valid():
models.Classes.objects.create(**obj.cleaned_data)
return redirect('/school/classes/')
return render(request, 'add_classes.html', {'obj': obj})
#添加教师
def add_tch(request):
if request.method == 'GET':
obj = TchForm()
return render(request, 'add_teacher.html', {'obj': obj})
else:
obj = TchForm(request.POST)
if obj.is_valid():
tc = obj.cleaned_data.pop('t2c') # 获取教师任课班级id
tch_obj = models.Teacher.objects.create(name=obj.cleaned_data['name']) # 添加新教师姓名
tch_obj.t2c.add(*tc) # 添加新教师任课班级
return redirect('/school/teachers/')
return render(request, 'add_teacher.html', {'obj': obj})
#编辑班级
def edit_cls(request, nid):
if request.method == 'GET':
cls = models.Classes.objects.filter(id=nid).first()
obj = ClsForm(initial={'title': cls.title})
return render(request, 'edit_classes.html', {'nid': nid, 'obj': obj})
else:
obj = ClsForm(request.POST)
if obj.is_valid():
models.Classes.objects.filter(id=nid).update(**obj.cleaned_data)
return redirect('/school/classes/')
return render(request, 'edit_classes.html', {'nid': nid, 'obj': obj})
#编辑教师
def edit_tch(request, nid):
if request.method == 'GET':
tch = models.Teacher.objects.filter(id=nid).first()
v = tch.t2c.values_list('id') # 获取该教师任课班级的id
cls_ids = list(zip(*v))[0] if list(zip(*v)) else [] # 格式化为列表类型
obj = TchForm(initial={'name': tch.name, 't2c': cls_ids})
return render(request, 'edit_teacher.html', {'nid': nid, 'obj': obj})
else:
obj = TchForm(request.POST)
if obj.is_valid():
tc = obj.cleaned_data.pop('t2c') # 获取修改后的任课班级id
# models.Teacher.objects.filter(id=nid).update(name=obj.cleaned_data['name']) # 更新教师姓名方法1
tch_obj = models.Teacher.objects.filter(id=nid).first()
tch_obj.name = obj.cleaned_data['name'] # 更新教师姓名方法2
tch_obj.save()
tch_obj.t2c.set(tc)
return redirect('/school/teachers/')
return render(request, 'edit_teacher.html', {'nid': nid, 'obj': obj})
|
3. html文件
classe：
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
|
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>班级列表</title>
<link rel="stylesheet" href="/static/plugins/bootstrap-3.3.7-dist/css/bootstrap.css" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >
</head>
<body>
<div style="width: 700px; margin: 30px auto">
<a class="btn btn-default" href="/school/add_cls/" rel="external nofollow" style="margin-bottom: 10px">添加班级</a>
<table class="table table-hover" border="1" cellspacing="0">
<thead>
<tr>
<th>ID</th>
<th>班级</th>
<th>操作</th>
</tr>
</thead>
<tbody>
{% for item in cls_list %}
<tr>
<td>{{ item.id }}</td>
<td>{{ item.title }}</td>
<td><a href="/school/edit_cls/{{ item.id }}" rel="external nofollow" >编辑</a></td>
</tr>
{% endfor %}
</tbody>
</table>
</div>
</body>
</html>
|
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
|
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>添加班级</title>
</head>
<body>
<h1>添加班级</h1>
<form action="/school/add_cls/" method="post">
{% csrf_token %}
<p>
{{ obj.title }} {{ obj.errors.title.0 }}
</p>
<input type="submit" value="提交">
</form>
</body>
</html>
|
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
|
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>编辑班级</title>
</head>
<body>
<h1>编辑班级</h1>
<form action="/school/edit_cls/{{ nid }}" method="post">
{% csrf_token %}
<p>
{{ obj.title }} {{ obj.errors.title.0 }}
</p>
<input type="submit" value="提交">
</form>
</body>
</html>
|
teachers：
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
|
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>教师列表</title>
<link rel="stylesheet" href="/static/plugins/bootstrap-3.3.7-dist/css/bootstrap.css" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >
</head>
<body>
<div style="width: 700px; margin: 30px auto">
<a class="btn btn-default" href="/school/add_tch/" rel="external nofollow" style="margin-bottom: 10px">添加教师</a>
<table class="table table-hover" border="1" cellspacing="0">
<thead>
<tr>
<th>ID</th>
<th>姓名</th>
<th>任教班级</th>
<th>操作</th>
</tr>
</thead>
<tbody>
{% for item in tch_list %}
<tr>
<td>{{ item.id }}</td>
<td>{{ item.name }}</td>
<td>
{% for row in item.t2c.all %}
<span style="border: solid gray 1px">{{ row.title }}</span>
{% endfor %}
</td>
<td><a href="/school/edit_tch/{{ item.id }}" rel="external nofollow" >编辑</a></td>
</tr>
{% endfor %}
</tbody>
</table>
</div>
</body>
</html>
|
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
|
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>添加教师</title>
<link rel="stylesheet" href="/static/plugins/bootstrap-3.3.7-dist/css/bootstrap.css" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >
</head>
<body>
<div style="width: 500px; margin: 20px auto">
<h3 style="width: 100px; margin: 10px auto">添加教师</h3>
<form class="form-horizontal" action="/school/add_tch/" method="post">
{% csrf_token %}
<div class="form-group">
<label class="col-sm-2 control-label">姓名</label>
<div class="col-sm-10">
{{ obj.name }} {{ obj.errors.name.0 }}
</div>
</div>
<div class="form-group">
<label class="col-sm-2 control-label">班级</label>
<div class="col-sm-10">
{{ obj.t2c }} {{ obj.errors.t2c.0 }}
</div>
</div>
<div class="form-group">
<div class="col-sm-offset-2 col-sm-10">
<input type="submit" class="btn btn-default" value="提交"></input>
</div>
</div>
</form>
</div>
</body>
</html>
|
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
|
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>编辑教师</title>
<link rel="stylesheet" href="/static/plugins/bootstrap-3.3.7-dist/css/bootstrap.css" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >
</head>
<body>
<div style="width: 500px; margin: 20px auto">
<h3 style="width: 100px; margin: 10px auto">编辑教师</h3>
<form class="form-horizontal" action="/school/edit_tch/{{ nid }}" method="post">
{% csrf_token %}
<div class="form-group">
<label class="col-sm-2 control-label">姓名</label>
<div class="col-sm-10">
{{ obj.name }} {{ obj.errors.name.0 }}
</div>
</div>
<div class="form-group">
<label class="col-sm-2 control-label">班级</label>
<div class="col-sm-10">
{{ obj.t2c }} {{ obj.errors.t2c.0 }}
</div>
</div>
<div class="form-group">
<div class="col-sm-offset-2 col-sm-10">
<input type="submit" class="btn btn-default" value="提交"></input>
</div>
</div>
</form>
</div>
</body>
</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
修改TchForm类
|
1
2
3
4
5
6
7
8
9
10
|
#教师表单验证规则
class TchForm(Form):
name = fields.CharField(max_length=16, min_length=2, widget=widgets.TextInput(attrs={'class': 'form-control'}))
t2c = fields.MultipleChoiceField(
# choices=models.Classes.objects.values_list('id', 'title'),
widget=widgets.SelectMultiple(attrs={'class': 'form-control'})
)
def __init__(self, *args, **kwargs): # 自定义__init__
super(TchForm, self).__init__(*args, **kwargs) # 调用父类的__init__
self.fields['t2c'].choices = models.Classes.objects.values_list('id', 'title') # 为字段t2c的choices赋值
|
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
修改TchForm类
|
1
2
3
4
5
6
7
8
9
10
|
#教师表单验证规则
from django.forms import models as form_models # 导入django.forms.models
class TchForm(Form):
name = fields.CharField(max_length=16, min_length=2, widget=widgets.TextInput(attrs={'class': 'form-control'}))
#重新定义字段
t2c = form_models.ModelMultipleChoiceField(
# choices=models.Classes.objects.values_list('id', 'title'),
queryset=models.Classes.objects.all(), # 利用queryset连接数据库，只能连接object类型
widget=widgets.SelectMultiple(attrs={'class': 'form-control'})
)
|
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。
设置models.py中的Classes类的返回值
|
1
2
3
4
|
class Classes(models.Model):
title = models.CharField(max_length=32)
def __str__(self):
return self.title
|
在班级表中新增一条记录
再在教师表中添加
以上所述是小编给大家介绍的使用Django Form解决表单数据无法动态刷新的两种方法，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对服务器之家网站的支持！
原文链接：http://www.cnblogs.com/OldJack/p/7121510.html