Flask-WTForms

Posted 2020-10-22 ゛竹先森゜

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what‘s the WTForms

　　WTForms是一个支持多个web框架的form组件，主要用于对用户请求数据进行验证。其作用是可以为轻量级的框架提供类似Django的form的功能。

安装：

pip3 install wtforms

源码流程分析

实例化流程分析

# 源码流程
    1. 执行type的 __call__ 方法，读取字段到静态字段 cls._unbound_fields 中； meta类读取到cls._wtforms_meta中
    2. 执行构造方法
        
        a. 循环cls._unbound_fields中的字段，并执行字段的bind方法，然后将返回值添加到 self._fields[name] 中。
            即：
                _fields = {
                    name: wtforms.fields.core.StringField(),
                }
                
            PS：由于字段中的__new__方法，实例化时：name = simple.StringField(label=‘用户名‘)，创建的是UnboundField(cls, *args, **kwargs)，当执行完bind之后，才变成执行 wtforms.fields.core.StringField()
        
        b. 循环_fields，为对象设置属性
            for name, field in iteritems(self._fields):
                # Set all the fields to attributes so that they obscure the class
                # attributes with the same names.
                setattr(self, name, field)
        c. 执行process，为字段设置默认值：self.process(formdata, obj, data=data, **kwargs)
            优先级：obj,data,formdata;
            
            再循环执行每个字段的process方法，为每个字段设置值：
            for name, field, in iteritems(self._fields):
                if obj is not None and hasattr(obj, name):
                    field.process(formdata, getattr(obj, name))
                elif name in kwargs:
                    field.process(formdata, kwargs[name])
                else:
                    field.process(formdata)
            
            执行每个字段的process方法，为字段的data和字段的raw_data赋值
            def process(self, formdata, data=unset_value):
                self.process_errors = []
                if data is unset_value:
                    try:
                        data = self.default()
                    except TypeError:
                        data = self.default
        
                self.object_data = data
        
                try:
                    self.process_data(data)
                except ValueError as e:
                    self.process_errors.append(e.args[0])
        
                if formdata:
                    try:
                        if self.name in formdata:
                            self.raw_data = formdata.getlist(self.name)
                        else:
                            self.raw_data = []
                        self.process_formdata(self.raw_data)
                    except ValueError as e:
                        self.process_errors.append(e.args[0])
        
                try:
                    for filter in self.filters:
                        self.data = filter(self.data)
                except ValueError as e:
                    self.process_errors.append(e.args[0])
                
        d. 页面上执行print(form.name) 时，打印标签
            
            因为执行了：
                字段的 __str__ 方法
                字符的 __call__ 方法
                self.meta.render_field(self, kwargs)
                    def render_field(self, field, render_kw):
                        other_kw = getattr(field, ‘render_kw‘, None)
                        if other_kw is not None:
                            render_kw = dict(other_kw, **render_kw)
                        return field.widget(field, **render_kw)
                执行字段的插件对象的 __call__ 方法，返回标签字符串

View Code

验证流程分析

a. 执行form的validate方法，获取钩子方法
            def validate(self):
                extra = {}
                for name in self._fields:
                    inline = getattr(self.__class__, ‘validate_%s‘ % name, None)
                    if inline is not None:
                        extra[name] = [inline]
        
                return super(Form, self).validate(extra)
        b. 循环每一个字段，执行字段的 validate 方法进行校验(参数传递了钩子函数)
            def validate(self, extra_validators=None):
                self._errors = None
                success = True
                for name, field in iteritems(self._fields):
                    if extra_validators is not None and name in extra_validators:
                        extra = extra_validators[name]
                    else:
                        extra = tuple()
                    if not field.validate(self, extra):
                        success = False
                return success
        c. 每个字段进行验证时候
            字段的pre_validate 【预留的扩展】
            字段的_run_validation_chain，对正则和字段的钩子函数进行校验
            字段的post_validate【预留的扩展】

View Code

用户登录注册示例

1. 用户登录

　　当用户登录时候，需要对用户提交的用户名和密码进行多种格式校验。如：

　　用户不能为空；用户长度必须大于6；

　　密码不能为空；密码长度必须大于12；密码必须包含字母、数字、特殊字符等（自定义正则）；

#!/usr/bin/env python
# -*- coding:utf-8 -*-
from flask import Flask, render_template, request, redirect
from wtforms import Form
from wtforms.fields import core
from wtforms.fields import html5
from wtforms.fields import simple
from wtforms import validators
from wtforms import widgets

app = Flask(__name__, template_folder=‘templates‘)
app.debug = True


class LoginForm(Form):
    name = simple.StringField(
        label=‘用户名‘,
        validators=[
            validators.DataRequired(message=‘用户名不能为空.‘),
            validators.Length(min=6, max=18, message=‘用户名长度必须大于%(min)d且小于%(max)d‘)
        ],
        widget=widgets.TextInput(),
        render_kw={‘class‘: ‘form-control‘}

    )
    pwd = simple.PasswordField(
        label=‘密码‘,
        validators=[
            validators.DataRequired(message=‘密码不能为空.‘),
            validators.Length(min=8, message=‘用户名长度必须大于%(min)d‘),
            validators.Regexp(regex="^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[[email protected]$!%*?&])[A-Za-z\[email protected]$!%*?&]{8,}",
                              message=‘密码至少8个字符，至少1个大写字母，1个小写字母，1个数字和1个特殊字符‘)

        ],
        widget=widgets.PasswordInput(),
        render_kw={‘class‘: ‘form-control‘}
    )



@app.route(‘/login‘, methods=[‘GET‘, ‘POST‘])
def login():
    if request.method == ‘GET‘:
        form = LoginForm()
        return render_template(‘login.html‘, form=form)
    else:
        form = LoginForm(formdata=request.form)
        if form.validate():
            print(‘用户提交数据通过格式验证，提交的值为：‘, form.data)
        else:
            print(form.errors)
        return render_template(‘login.html‘, form=form)

if __name__ == ‘__main__‘:
    app.run()

app.py

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<h1>登录</h1>
<form method="post">
    <!--<input type="text" name="name">-->
    <p>{{form.name.label}} {{form.name}} {{form.name.errors[0] }}</p>

    <!--<input type="password" name="pwd">-->
    <p>{{form.pwd.label}} {{form.pwd}} {{form.pwd.errors[0] }}</p>
    <input type="submit" value="提交">
</form>
</body>
</html>

2. 用户注册

　　注册页面需要让用户输入：用户名、密码、密码重复、性别、爱好等。

from flask import Flask, render_template, request, redirect
from wtforms import Form
from wtforms.fields import core
from wtforms.fields import html5
from wtforms.fields import simple
from wtforms import validators
from wtforms import widgets

app = Flask(__name__, template_folder=‘templates‘)
app.debug = True



class RegisterForm(Form):
    name = simple.StringField(
        label=‘用户名‘,
        validators=[
            validators.DataRequired()
        ],
        widget=widgets.TextInput(),
        render_kw={‘class‘: ‘form-control‘},
        default=‘alex‘
    )

    pwd = simple.PasswordField(
        label=‘密码‘,
        validators=[
            validators.DataRequired(message=‘密码不能为空.‘)
        ],
        widget=widgets.PasswordInput(),
        render_kw={‘class‘: ‘form-control‘}
    )

    pwd_confirm = simple.PasswordField(
        label=‘重复密码‘,
        validators=[
            validators.DataRequired(message=‘重复密码不能为空.‘),
            validators.EqualTo(‘pwd‘, message="两次密码输入不一致")
        ],
        widget=widgets.PasswordInput(),
        render_kw={‘class‘: ‘form-control‘}
    )

    email = html5.EmailField(
        label=‘邮箱‘,
        validators=[
            validators.DataRequired(message=‘邮箱不能为空.‘),
            validators.Email(message=‘邮箱格式错误‘)
        ],
        widget=widgets.TextInput(input_type=‘email‘),
        render_kw={‘class‘: ‘form-control‘}
    )

    gender = core.RadioField(
        label=‘性别‘,
        choices=(
            (1, ‘男‘),
            (2, ‘女‘),
        ),
        coerce=int
    )
    city = core.SelectField(
        label=‘城市‘,
        choices=(
            (‘bj‘, ‘北京‘),
            (‘sh‘, ‘上海‘),
        )
    )

    hobby = core.SelectMultipleField(
        label=‘爱好‘,
        choices=(
            (1, ‘篮球‘),
            (2, ‘足球‘),
        ),
        coerce=int
    )

    favor = core.SelectMultipleField(
        label=‘喜好‘,
        choices=(
            (1, ‘篮球‘),
            (2, ‘足球‘),
        ),
        widget=widgets.ListWidget(prefix_label=False),
        option_widget=widgets.CheckboxInput(),
        coerce=int,
        default=[1, 2]
    )

    def __init__(self, *args, **kwargs):
        super(RegisterForm, self).__init__(*args, **kwargs)
        self.favor.choices = ((1, ‘篮球‘), (2, ‘足球‘), (3, ‘羽毛球‘))

    def validate_pwd_confirm(self, field):
        """
        自定义pwd_confirm字段规则，例：与pwd字段是否一致
        :param field: 
        :return: 
        """
        # 最开始初始化时，self.data中已经有所有的值

        if field.data != self.data[‘pwd‘]:
            # raise validators.ValidationError("密码不一致") # 继续后续验证
            raise validators.StopValidation("密码不一致")  # 不再继续后续验证


@app.route(‘/register‘, methods=[‘GET‘, ‘POST‘])
def register():
    if request.method == ‘GET‘:
        form = RegisterForm(data={‘gender‘: 1})
        return render_template(‘register.html‘, form=form)
    else:
        form = RegisterForm(formdata=request.form)
        if form.validate():
            print(‘用户提交数据通过格式验证，提交的值为：‘, form.data)
        else:
            print(form.errors)
        return render_template(‘register.html‘, form=form)



if __name__ == ‘__main__‘:
    app.run()

app.py

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<h1>用户注册</h1>
<form method="post" novalidate style="padding:0  50px">
    {% for item in form %}
    <p>{{item.label}}: {{item}} {{item.errors[0] }}</p>
    {% endfor %}
    <input type="submit" value="提交">
</form>
</body>
</html>

metaclass知识点

　　metaclass是创建类的元类，即一般的类是metaclass的对象，在类被解释的时候就会触发其元类的__init__方法，而类被实例化的时候，会先执行元类的__call__方法再执行自己的__new__方法最后才执行自己的__init__方法

#方式一：
class MyType(type):
    def __init__(self, *args, **kwargs):
        print(‘MyType创建类‘,self)
        super(MyType, self).__init__(*args, **kwargs)

    def __call__(self, *args, **kwargs):
        obj = super(MyType, self).__call__(*args, **kwargs)
        print(‘类创建对象‘, self, obj)
        return obj


class Foo(object,metaclass=MyType):
    user = ‘wupeiqi‘
    age = 18

obj = Foo()



#方式二：
class MyType(type):
    def __init__(self, *args, **kwargs):
        super(MyType, self).__init__(*args, **kwargs)

    def __call__(cls, *args, **kwargs):
        v = dir(cls)
        obj = super(MyType, cls).__call__(*args, **kwargs)
        return obj


class Foo(MyType(‘MyType‘, (object,), {})):
    user = ‘wupeiqi‘
    age = 18


obj = Foo()




#方式三：
class MyType(type):
    def __init__(self, *args, **kwargs):
        super(MyType, self).__init__(*args, **kwargs)

    def __call__(cls, *args, **kwargs):
        v = dir(cls)
        obj = super(MyType, cls).__call__(*args, **kwargs)
        return obj


def with_metaclass(arg,base):
    return MyType(‘MyType‘, (base,), {})


class Foo(with_metaclass(MyType,object)):
    user = ‘wupeiqi‘
    age = 18


obj = Foo()

metaclass创建类的三种方式

自定义form

　　form组件其实由三大部分组成：类、字段、插件。所以我们要自定义form，就自定义这三部分就行。

from flask import Flask, render_template, request, redirect,Markup
app = Flask(__name__, template_folder=‘templates‘)
import wtforms
app.debug = True

# 插件
class Widget(object):
    #基类
    pass

class InputText(Widget):
    # input插件
    def __call__(self, *args, **kwargs):
        return "<input type=‘text‘ name=‘name‘ />"

class TextArea(Widget):
    # textarea插件
    def __call__(self, *args, **kwargs):
        return "<textarea name=‘email‘> </textarea>"

# Form类
class BaseForm(object):
    def __init__(self):
        # 获取当前字段
        _fields = {}
        for name,field in self.__class__.__dict__.items():
            if isinstance(field,Field):
                _fields[name] = field
        self._fields = _fields
        self.data = {}


    def validate(self,request_data):
        # 找到所有的字段，执行每个字段的validate方法
        flag = True
        for name,field in self._fields.items():
            # 123
            input_val = request_data.get(name,‘‘)
            result = field.validate(input_val)
            if not result:
                flag = False
            else:
                self.data[name] = input_val
        return flag
# 字段
class Field(object):

    def __str__(self):
        return Markup(self.widget())

class StringField(Field):
    widget = InputText()

    def validate(self,val):
        if val:
            return True

class EmailField(Field):
    widget = TextArea() # EmailField.widget/ self.widget
    reg = ".*@.*"

    def validate(self, val):
        import re
        if re.match(self.reg,val):
            return True

########## 使用 ###############
class LoginForm(BaseForm):
    name = StringField()
    email = EmailField()


@app.route(‘/login‘, methods=[‘GET‘, ‘POST‘])
def login():

    form = LoginForm()
    ret = form.validate(request.form)
    print("验证成功",ret)
    print("验证成功值",form.data)
    # print(obj.name)
    # print(obj.email)
    return render_template(‘login.html‘,form=form)

if __name__ == ‘__main__‘:
    app.run()

app.py

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<form method="post">
    {{ form.name }}
    {{ form.email }}
    <input type="submit" value="提交">
    </form>
</body>
</html>

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