TypeError：“UnboundField”对象不能用 Flask 调用答案

【问题标题】：TypeError: 'UnboundField' object is not callable with FlaskTypeError：“UnboundField”对象不能用 Flask 调用
【发布时间】：2021-05-01 09:26:47
【问题描述】：

我正在运行 Flask 版本 1.1.2

我的注册表单有以下代码

from flask_wtf import FlaskForm
from wtforms import StringField, PasswordField, SubmitField, BooleanField
from wtforms.validators import DataRequired, Length, EqualTo, Email

class RegistrationForm(FlaskForm):
    def __init__(self):
        self.username = StringField("Username", validators=[DataRequired(), Length(min=2, max=20)])
        self.email = StringField("EMail", validators = [DataRequired(), Email()])
        self.password = PasswordField("Password", validators = [DataRequired(), Length(min = 5)])
        self.confirm_password = PasswordField("Confirm password", validators = [DataRequired(), EqualTo("password")])
        self.submit = SubmitField("Sign Up")

这是注册页面：

{% extends "layout.html" %}
{% block content %}
    <div class="content-section">
      <form method="POST" action="">


        <fieldset class = "form-group">
          <legend class="border-bottom mb-4">Sign In</legend>

          <div class="form-group">
            {{ form.username(class="form-control form-control-lg") }}
          </div>
          <div class="form-group">
            {{ form.email(class="form-control form-control-lg") }}
          </div>
          <div class="form-group">
            {{ form.password(class="form-control form-control-lg") }}
          </div>
          <div class="form-group">
            {{ form.confirm_password(class="form-control form-control-lg") }}
          </div>
        </fieldset>

        <div class="form-group">
          {{ form.submit(class="btn btn-outline-info") }}
        </div>
    </div>

    <div class="border-top pt-3">
      <small class="text-muted">
        Already have an account? <a class="ml-2" href="{{ url_for('register') }}">Sign in </a>
      </small>


{% endblock content %}

但是，当我尝试访问注册页面时，出现以下错误：

  File "D:\xy\-Python\Modules\Flask\Flask_Blog\templates\register.html", line 1, in top-level template code
    {% extends "layout.html" %}
  File "D:\xy\-Python\Modules\Flask\Flask_Blog\templates\layout.html", line 43, in top-level template code
    {% block content %}{% endblock %}
  File "D:\xy\-Python\Modules\Flask\Flask_Blog\templates\register.html", line 11, in block "content"
    {{ form.username(class="form-control form-control-lg") }}
TypeError: 'UnboundField' object is not callable

（上面至少还有 20 行）

【问题讨论】：

标签： python forms flask jinja2 wtforms

【解决方案1】：

您应该如下更改类符号。这适用于您要添加类的所有字段。请参阅https://wtforms.readthedocs.io/en/2.3.x/fields/ 上的文档

{{ form.username(class_="form-control form-control-lg") }}

并将您的表单更改为以下内容，请参阅https://flask-wtf.readthedocs.io/en/stable/quickstart.html#creating-forms

class RegistrationForm(FlaskForm):
    username = StringField("Username", validators=[DataRequired(), Length(min=2, max=20)])
    email = StringField("EMail", validators = [DataRequired(), Email()])
    password = PasswordField("Password", validators = [DataRequired(), Length(min = 5)])
    confirm_password = PasswordField("Confirm password", validators = [DataRequired(), EqualTo("password")])
    submit = SubmitField("Sign Up")

【讨论】：

我改变了它，但仍然得到同样的错误。当我将 print(type(self.username)) 放入 RegistrationForm 的构造函数中时，它会打印：“”。