Flask wtforms ValidationError 未向用户显示

Question

我正在使用带有输入验证的烧瓶 wtforms。一切正常，除了验证失败，我的 ValidationError 消息没有显示给用户...

from flask_wtf import FlaskForm
from wtforms import StringField, SubmitField, PasswordField, ValidationError # URLField, EmailField
from wtforms.validators import DataRequired, Email, EqualTo

class SignupForm(FlaskForm):
    name = StringField("Name:", validators=[DataRequired()])
    email = StringField("Email:", validators=[DataRequired(), Email()])
    password = PasswordField("Password:", validators=[DataRequired(), EqualTo('pass_confirm', message='Passwords must match')])
    pass_confirm = PasswordField("Confirm:", validators=[DataRequired()])
    submit = SubmitField("Create Account")

    def validate_email(self, field):
        if User.query.filter_by(email=field.data).first():
            raise ValidationError('Your email has already been registered.')

    def validate_name(self, field):
        if User.query.filter_by(name=field.data).first():
            raise ValidationError('This username is taken.')

在我看来：

@users.route('/signup', methods=['GET','POST'])
def signup():
    form = SignupForm()

    if form.validate_on_submit():
        url = form.name.data # todo: generate unique url
        user = User(name=form.name.data,
                    url=url,
                    email = form.email.data,
                    password = form.password.data)
        db.session.add(user)
        db.session.commit()

        return redirect(url_for('users.login'))

    return render_template('signup.html', form=form)

这是模板：

<div class="jumbotron">
  <h1>Sign up Page</h1>
  <p>Please fill out the form</p>
  <form method="POST">
    {{ form.hidden_tag() }}
    <div class="form-group">
      {{ form.name.label(class='form-group') }}
      {{ form.name(class='form-control') }}
    </div>

    <div class="form-group">
      {{ form.email.label(class='form-group') }}
      {{ form.email(class='form-control') }}
    </div>

    <div class="form-group">
      {{ form.password.label(class='form-group') }}
      {{ form.password(class='form-control') }}
    </div>

    <div class="form-group">
      {{ form.pass_confirm.label(class='form-group') }}
      {{ form.pass_confirm(class='form-control') }}
    </div>

      {{ form.submit(class='btn btn-primary') }}
  </form>

</div>

提交无效的表单（无效的电子邮件或姓名）后，表单只会返回空白，而不会指出用户做错了什么。如何向用户显示这些验证错误？非常感谢！

Answer 1

表单必须获取一些数据

@users.route('/signup', methods=['GET','POST'])
def signup():
    form = SignupForm(request.form)

或

@users.route('/signup', methods=['GET','POST'])
def signup():
    form = SignupForm(request.json)

Answer 2

我相信您错误地导入了 ValidationError 试试这个从 wtforms.validators 导入它 ->

from flask_wtf import FlaskForm
from wtforms import StringField, SubmitField, PasswordField # URLField, EmailField
from wtforms.validators import DataRequired, Email, EqualTo, ValidationError

除此之外，您还可以从您的路线代码中将 Flash 消息添加到屏幕上。

from flask import flash
if form.validate_on_submit():
    flash(f'Info was saved to the database for user {form.name.data}', success)
else:
    flash('Failed to save to database', 'danger')