Flask之wtforms源码分析

一、wtforms源码流程

1、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

2、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】

二、自定义Form组件

#!usr/bin/env python
# -*- coding:utf-8 -*-
from flask import Flask,render_template,request,Markup
app = Flask(__name__,template_folder="templates")
app.debug = True
# ==============通过这几个类就可以显示了-==============
#插件
class Widget(object):
    pass

class InputText(Widget):
    def __call__(self, *args, **kwargs):

        return "<input type='text' name='name'>"

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

#Form
class BaseForm(object):
    def __init__(self):
        #获取当前所有的字段
        _fields = {}
        for name, field in self.__class__.__dict__.items():
            if isinstance(field, Field):  # 筛选出字段是name和emailDe
                _fields[name] = field
        self._fields = _fields
        self.data = {}
        # print(_fields)  # {'name': 111, 'email': 222}

    def validate(self,request_data):
        #先找到所有的字段，在执行每一个字段的validate方法
        flag = True
        for name, field in self._fields.items():
            input_val = request_data.get(name,"") #用户输入的值
            result= field.validate(input_val)  #每一个字段自己校验
            print("???????????",input_val,result)
            if not result:
                flag = False
            else:
                self.data[name] = input_val
        return flag
#字段
class Field(object):
    '''所有类的基类'''
    def __str__(self):          #python中的静态字段通过类能找到，通过对象也能找到
        return Markup(self.widget())  #self就是StringField，self

class StringField(Field):  #每个字段打印的时候都要去执行__str__，所以选择放在基类里面，自己没有就调用父类的
    widget = InputText()
    def validate(self,val):
        if val:
            return True

class EmaliField(Field):
    widget = TextArea()
    reg = ".*@.*"

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

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

@app.route('/index', methods=["GET","POST"])
def index():
    form = LoginForm()
    ret = form.validate(request.form)
    print("验证成功",ret)
    print("验证成功的值",form.data)
    # print(form.name)
    # print(form.email)
    return render_template("index.html",form=form)

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