Form介绍

　　之前在HTML页面中利用form表单向后端提交数据时，都会写一些获取用户输入的标签并且用form标签把它们包起来。

与此同时我们在好多场景下都需要对用户的输入做校验，比如校验用户是否输入，输入的长度和格式等正不正确。如果用户输入的内容有错误就需要在页面上相应的位置显示显示对应的错误信息.。

Django form组件就实现了上面所述的功能。

总结一下，其实form组件的主要功能如下:

生成页面可用的HTML标签
对用户提交的数据进行校验
保留上次输入内容

普通的登录

views.py

def login(request):error_msg = ""if request.method == "POST":username = request.POST.get("username")pwd = request.POST.get("pwd")if username == "SKS" and pwd == "1366768":return HttpResponse("OK")else:error_msg = "用户名或密码错误"return render(request, "login.html", {"error_msg": error_msg})

login.html

<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><meta http-equiv="x-ua-compatible" content="IE=edge"><meta name="viewport" content="width=device-width, initial-scale=1"><title>login</title><style>.error {color: red;}</style>
</head>
<body>
<form action="/login/" method="post">{% csrf_token %}<p><label for="username">用户名</label><input type="text" name="username" id="username"></p><p><label for="pwd">密码</label><input type="password" name="pwd" id="pwd"><span class="error"></span></p><p><input type="submit"><span class="error">{{ error_msg }}</span></p>
</form>
</body>
</html>

使用form组件

views.py

先定义好一个LoginForm类。

# 定义一个form组件类
class LoginForm(forms.Form):# 验证的字段及条件username = forms.CharField(min_length=8, label="用户名")pwd = forms.CharField(min_length=6, label="密码")def login2(request):# 存储错误信息error_msg = ""# 实例化对象form_obj = LoginForm()# 判断前端页面请求是否是POST请求if request.method == "POST":# 将数据传入form组件类中form_obj = LoginForm(request.POST)# 存储的正确信息if form_obj.is_valid():username = form_obj.cleaned_data.get("username")pwd = form_obj.cleaned_data.get("pwd")if username == "SKS" and pwd == "1866768":return HttpResponse("OK")else:error_msg = "用户名或密码错误"return render(request, "login2.html", {"form_obj": form_obj, "error_msg": error_msg})

login2.html

<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><meta http-equiv="x-ua-compatible" content="IE=edge"><meta name="viewport" content="width=device-width, initial-scale=1"><title>login</title><style>.error {color: red;}</style>
</head>
<body>
<form action="/login2/" method="post" novalidate>{% csrf_token %}<p>{{ form_obj.username.label }}{{ form_obj.username }}<span class="error">{{ form_obj.username.errors.0 }}</span></p><p>{{ form_obj.pwd.label }}{{ form_obj.pwd }}<span class="error">{{ form_obj.pwd.errors.0 }}</span></p><p><input type="submit"><span class="error">{{ error_msg }}</span></p>
</form>
</body>
</html>

看网页效果发现也验证了form的功能：
• 前端页面是form类的对象生成的 -->生成HTML标签功能
• 当用户名和密码输入为空或输错之后页面都会提示 -->用户提交校验功能
• 当用户输错之后再次输入上次的内容还保留在input框 -->保留上次输入内容

Form组件

常用字段演示

initial

初始值，input框里面的初始值。

# 定义一个类继承forms.Form
class LoginForm(forms.Form):username = forms.CharField(min_length=6,label="用户名",initial="hewm"  # 设置默认值方法
    )pwd = forms.CharField(min_length=6, label="密码")

error_messages

重写错误信息。

class LoginForm(forms.Form):username = forms.CharField(min_length=6,label="用户名",initial="hewm",# 重写错误提示信息error_messages={"required": "不能为空","invalid": "格式错误","min_length": "用户名最短6位"})pwd = forms.CharField(min_length=6, label="密码")

password

class LoginForm(forms.Form):...pwd = forms.CharField(min_length=6,label="密码",
         # 密文方法   参数attrs：样式类   render_value=验证失败是否回填

widget=forms.widgets.PasswordInput(attrs={'class': 'c1'}, render_value=True) )

radioSelect

单radio值为字符串

class LoginForm(forms.Form):username = forms.CharField(min_length=8,label="用户名",initial="hewm",error_messages={"required": "不能为空","invalid": "格式错误","min_length": "用户名最短8位"})pwd = forms.CharField(min_length=6, label="密码")gender = forms.fields.ChoiceField(choices=((1, "男"), (2, "女"), (3, "保密")),label="性别",initial=3,widget=forms.widgets.RadioSelect)

单选Select

class LoginForm(forms.Form):...hobby = forms.fields.ChoiceField(choices=((1, "篮球"), (2, "足球"), (3, "乒乓球"), ),label="爱好",initial=3,widget=forms.widgets.Select)

多选Select

class LoginForm(forms.Form):...hobby = forms.fields.MultipleChoiceField(choices=((1, "篮球"), (2, "足球"), (3, "双色球"), ),label="爱好",initial=[1, 3],widget=forms.widgets.SelectMultiple)

单选checkbox

class LoginForm(forms.Form):...keep = forms.fields.ChoiceField(label="是否记住密码",initial="checked",widget=forms.widgets.CheckboxInput)

多选checkbox

class LoginForm(forms.Form):...hobby = forms.fields.MultipleChoiceField(choices=((1, "篮球"), (2, "足球"), (3, "双色球"),),label="爱好",initial=[1, 3],widget=forms.widgets.CheckboxSelectMultiple)

关于choice的注意事项：

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。

方式一：

from django.forms import Form
from django.forms import widgets
from django.forms import fieldsclass MyForm(Form):user = fields.ChoiceField(# choices=((1, '上海'), (2, '北京'),),initial=2,widget=widgets.Select)# 初始化init方法 （执行时间为类实例化时执行）def __init__(self, *args, **kwargs):super(MyForm,self).__init__(*args, **kwargs)# self.fields['user'].widget.choices = ((1, '上海'), (2, '北京'),)# 或self.fields['user'].widget.choices = models.Classes.objects.all().values_list('id','caption')

方法二

from django import forms
from django.forms import fields
from django.forms import models as form_modelclass FInfo(forms.Form):authors = form_model.ModelMultipleChoiceField(queryset=models.NNewType.objects.all())# authors = form_model.ModelChoiceField(queryset=models.NNewType.objects.all())

Fieldrequired=True,               是否允许为空widget=None,                 HTML插件label=None,                  用于生成Label标签或显示内容initial=None,                初始值help_text='',                帮助信息(在标签旁边显示)error_messages=None,         错误信息 {'required': '不能为空', 'invalid': '格式错误'}show_hidden_initial=False,   是否在当前插件后面再加一个隐藏的且具有默认值的插件（可用于检验两次输入是否一直）validators=[],               自定义验证规则localize=False,              是否支持本地化disabled=False,              是否可以编辑label_suffix=None            Label内容后缀CharField(Field)max_length=None,             最大长度min_length=None,             最小长度strip=True                   是否移除用户输入空白IntegerField(Field)max_value=None,              最大值min_value=None,              最小值FloatField(IntegerField)...DecimalField(IntegerField)max_value=None,              最大值min_value=None,              最小值max_digits=None,             总长度decimal_places=None,         小数位长度BaseTemporalField(Field)input_formats=None          时间格式化   DateField(BaseTemporalField)    格式：2015-09-01
TimeField(BaseTemporalField)    格式：11:12
DateTimeField(BaseTemporalField)格式：2015-09-01 11:12DurationField(Field)            时间间隔：%d %H:%M:%S.%f...RegexField(CharField)regex,                      自定制正则表达式max_length=None,            最大长度min_length=None,            最小长度error_message=None,         忽略，错误信息使用 error_messages={'invalid': '...'}EmailField(CharField)      ...FileField(Field)allow_empty_file=False     是否允许空文件ImageField(FileField)      ...注：需要PIL模块，pip3 install Pillow以上两个字典使用时，需要注意两点：- form表单中 enctype="multipart/form-data"- view函数中 obj = MyForm(request.POST, request.FILES)URLField(Field)...BooleanField(Field)  ...NullBooleanField(BooleanField)...ChoiceField(Field)...choices=(),                选项，如：choices = ((0,'上海'),(1,'北京'),)required=True,             是否必填widget=None,               插件，默认select插件label=None,                Label内容initial=None,              初始值help_text='',              帮助提示ModelChoiceField(ChoiceField)...                        django.forms.models.ModelChoiceFieldqueryset,                  # 查询数据库中的数据empty_label="---------",   # 默认空显示内容to_field_name=None,        # HTML中value的值对应的字段limit_choices_to=None      # ModelForm中对queryset二次筛选
     
ModelMultipleChoiceField(ModelChoiceField)...                        django.forms.models.ModelMultipleChoiceFieldTypedChoiceField(ChoiceField)coerce = lambda val: val   对选中的值进行一次转换empty_value= ''            空值的默认值MultipleChoiceField(ChoiceField)...TypedMultipleChoiceField(MultipleChoiceField)coerce = lambda val: val   对选中的每一个值进行一次转换empty_value= ''            空值的默认值ComboField(Field)fields=()                  使用多个验证，如下：即验证最大长度20，又验证邮箱格式fields.ComboField(fields=[fields.CharField(max_length=20), fields.EmailField(),])MultiValueField(Field)PS: 抽象类，子类中可以实现聚合多个字典去匹配一个值，要配合MultiWidget使用SplitDateTimeField(MultiValueField)input_date_formats=None,   格式列表：['%Y--%m--%d', '%m%d/%Y', '%m/%d/%y']input_time_formats=None    格式列表：['%H:%M:%S', '%H:%M:%S.%f', '%H:%M']FilePathField(ChoiceField)     文件选项，目录下文件显示在页面中path,                      文件夹路径match=None,                正则匹配recursive=False,           递归下面的文件夹allow_files=True,          允许文件allow_folders=False,       允许文件夹required=True,widget=None,label=None,initial=None,help_text=''GenericIPAddressFieldprotocol='both',           both,ipv4,ipv6支持的IP格式unpack_ipv4=False          解析ipv4地址，如果是::ffff:192.0.2.1时候，可解析为192.0.2.1， PS：protocol必须为both才能启用SlugField(CharField)           数字，字母，下划线，减号（连字符）...UUIDField(CharField)           uuid类型Django form内置字段

内置字段

校验

方式一：

from django.forms import Form
from django.forms import widgets
from django.forms import fields
from django.core.validators import RegexValidatorclass MyForm(Form):user = fields.CharField(validators=[RegexValidator(r'^[0-9]+$', '请输入数字'), RegexValidator(r'^159[0-9]+$', '数字必须以159开头')],)

方式二：

import re
from django.forms import Form
from django.forms import widgets
from django.forms import fields
from django.core.exceptions import ValidationError# 自定义验证规则
def mobile_validate(value):mobile_re = re.compile(r'^(13[0-9]|15[012356789]|17[678]|18[0-9]|14[57])[0-9]{8}$')if not mobile_re.match(value):raise ValidationError('手机号码格式错误')class PublishForm(Form):title = fields.CharField(max_length=20,min_length=5,error_messages={'required': '标题不能为空','min_length': '标题最少为5个字符','max_length': '标题最多为20个字符'},widget=widgets.TextInput(attrs={'class': "form-control",'placeholder': '标题5-20个字符'}))# 使用自定义验证规则phone = fields.CharField(validators=[mobile_validate, ],error_messages={'required': '手机不能为空'},widget=widgets.TextInput(attrs={'class': "form-control",'placeholder': u'手机号码'}))email = fields.EmailField(required=False,error_messages={'required': u'邮箱不能为空','invalid': u'邮箱格式错误'},widget=widgets.TextInput(attrs={'class': "form-control", 'placeholder': u'邮箱'}))

补充进阶

应用Bootstrap样式

<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><meta http-equiv="x-ua-compatible" content="IE=edge"><meta name="viewport" content="width=device-width, initial-scale=1"><link rel="stylesheet" href="/static/bootstrap/css/bootstrap.min.css"><title>login</title>
</head>
<body>
<div class="container"><div class="row"><form action="/login2/" method="post" novalidate class="form-horizontal">{% csrf_token %}<div class="form-group"><label for="{{ form_obj.username.id_for_label }}"class="col-md-2 control-label">{{ form_obj.username.label }}</label><div class="col-md-10">{{ form_obj.username }}<span class="help-block">{{ form_obj.username.errors.0 }}</span></div></div><div class="form-group"><label for="{{ form_obj.pwd.id_for_label }}" class="col-md-2 control-label">{{ form_obj.pwd.label }}</label><div class="col-md-10">{{ form_obj.pwd }}<span class="help-block">{{ form_obj.pwd.errors.0 }}</span></div></div><div class="form-group"><label class="col-md-2 control-label">{{ form_obj.gender.label }}</label><div class="col-md-10"><div class="radio">{% for radio in form_obj.gender %}<label for="{{ radio.id_for_label }}">{{ radio.tag }}{{ radio.choice_label }}</label>{% endfor %}</div></div></div><div class="form-group"><div class="col-md-offset-2 col-md-10"><button type="submit" class="btn btn-default">注册</button></div></div></form></div>
</div><script src="/static/jquery-3.2.1.min.js"></script>
<script src="/static/bootstrap/js/bootstrap.min.js"></script>
</body>
</html>Django form应用Bootstrap样式简单示例

代码示例

批量添加样式

可通过重写form类的init方法来实现。

class LoginForm(forms.Form):username = forms.CharField(min_length=8,label="用户名",initial="张三",error_messages={"required": "不能为空","invalid": "格式错误","min_length": "用户名最短8位"}...def __init__(self, *args, **kwargs):super(LoginForm, self).__init__(*args, **kwargs)for field in iter(self.fields):self.fields[field].widget.attrs.update({'class': 'form-control'})批量添加样式

代码示例

源码简易剖析

views.py文件

def register(request):if request.method == "POST":res = {"user": None, "error_dict": None}form = RegForm(request.POST)# 存储验证通过的信息.is_valid()（源码剖析开始点）if form.is_valid():user = form.cleaned_data.get("user")pwd = form.cleaned_data.get("pwd")email = form.cleaned_data.get("email")avatar = request.FILES.get("avatar")print(user,pwd,email,avatar)print("="*120)if avatar:user = UserInfo.objects.create_user(username=user, password=pwd, email=email, avatar=avatar)else:user = UserInfo.objects.create_user(username=user, password=pwd, email=email)res["user"] = user.usernameelse:print(form.errors)res["error_dict"] = form.errorsreturn JsonResponse(res)form = RegForm()return render(request, 'register.html', locals())

views.py

点击进入forms.py文件

    def is_valid(self):"""Returns True if the form has no errors. Otherwise, False. If errors arebeing ignored, returns False."""# 含义：返回布尔值，只要有数据并且没有错误信息就返回Truereturn self.is_bound and not self.errors

forms.py

点击self.errors进入forms.py文件中

# 静态方法
@propertydef errors(self):"Returns an ErrorDict for the data provided for the form"# 判断self._errors是否为空if self._errors is None:self.full_clean()return self._errors

def errors(self):

点击._errors进入forms.py文件中

    def __init__(self, data=None, files=None, auto_id='id_%s', prefix=None,initial=None, error_class=ErrorList, label_suffix=None,empty_permitted=False, field_order=None, use_required_attribute=None, renderer=None):self.is_bound = data is not None or files is not Noneself.data = data or {}self.files = files or {}self.auto_id = auto_idif prefix is not None:self.prefix = prefixself.initial = initial or {}self.error_class = error_class# Translators: This is the default suffix added to form field labelsself.label_suffix = label_suffix if label_suffix is not None else _(':')self.empty_permitted = empty_permitted# 默认值为Noneself._errors = None  # Stores the errors after clean() has been called.# The base_fields class attribute is the *class-wide* definition of# fields. Because a particular *instance* of the class might want to# alter self.fields, we create self.fields here by copying base_fields.# Instances should always modify self.fields; they should not modify# self.base_fields.self.fields = copy.deepcopy(self.base_fields)self._bound_fields_cache = {}self.order_fields(self.field_order if field_order is None else field_order)

__init__方法

返回def errors(self):

    @propertydef errors(self):"Returns an ErrorDict for the data provided for the form"if self._errors is None:self.full_clean()  # 这个方法才是真正帮忙执行效验操作return self._errors

返回errors方法

点击

    def full_clean(self):"""Cleans all of self.data and populates self._errors andself.cleaned_data."""self._errors = ErrorDict()  # 定义一个保存错误信息字典if not self.is_bound:  # Stop further processing.returnself.cleaned_data = {}# If the form is permitted to be empty, and none of the form data has# changed from the initial data, short circuit any validation.if self.empty_permitted and not self.has_changed():returnself._clean_fields()self._clean_form()self._post_clean()

full_clean方法

点击self._clean_fields()进入

    def _clean_fields(self):for name, field in self.fields.items():# self.fields：类似一个字典#for name, field in self.fields.items():解释分别获取self.fields的键和值分别赋值给 name, field# value_from_datadict() gets the data from the data dictionaries.# Each widget type knows how to retrieve its own data, because some# widgets split data over several HTML fields.if field.disabled:value = self.get_initial_for_field(field, name)else:value = field.widget.value_from_datadict(self.data, self.files, self.add_prefix(name))try:if isinstance(field, FileField):  # 如果是文件字段initial = self.get_initial_for_field(field, name)value = field.clean(value, initial)else:  #   field.clean(value) 之后Dbug运行检查，为循环判断错误value = field.clean(value)self.cleaned_data[name] = valueif hasattr(self, 'clean_%s' % name):value = getattr(self, 'clean_%s' % name)()self.cleaned_data[name] = valueexcept ValidationError as e:self.add_error(name, e)