python - 如何使用 Flask 和 WTForms 在保留表单数据的同时进行重定向？

Question

让我们创建一个带有注册表单的页面。它位于#registration 部分。如果用户提交无效数据，页面应将其返回到#registration部分并显示向哪些字段提交了无效值。

我尝试渲染模板并做出响应并重定向到它，但我收到了 TypeError:

  File ".../app/routes.py", line 28, in index
    return redirect(url_for('.index', form=form, _anchor='registration'), 302, response)
  File ".../python3.7/site-packages/werkzeug/utils.py", line 507, in redirect
    mimetype="text/html",
TypeError: __call__() got an unexpected keyword argument 'mimetype'

该函数如下所示:

@app.route('/', methods=['GET', 'POST'])
def index():
    form = RegisterForm()
    if form.validate_on_submit():
        # everithing OK
        return redirect(url_for('.index', _anchor='registration'))

    # If form was submitted but contained invalid information
    if form.is_submitted():
        response = make_response(render_template('index.html', form=form))
        return redirect(url_for('.index', _anchor='registration'), 302, response)

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

Answer 1

您无法发送带有重定向响应的内容，您只能说“转到此网址”。 Flask 还接受 Response 类，而不是实例作为重定向的参数。

要解决您的问题，您需要使用 session (或简单地flash)来保留请求之间的状态。

这是一个原型(prototype):

from flask import Flask, render_template_string, request, session, redirect
from werkzeug import MultiDict

from flask_wtf import FlaskForm
from wtforms import StringField, IntegerField
from wtforms.validators import AnyOf

app = Flask(__name__)
app.secret_key = 'secret'

class MyForm(FlaskForm):
    name = StringField('name', validators=[AnyOf(['secretname'])])

@app.route('/', methods=['POST', 'GET'])
def form_page():
    form = MyForm()
    html = '''
    {% for error in form.name.errors %} <span>{{ error }}</span> {% endfor %}
    <form method="POST" action="/">
        {{ form.csrf_token }}
        {{ form.name.label }} {{ form.name(size=20) }}
        <input type="submit" value="Go">
    </form>
    '''
    
    if request.method == 'GET':
        formdata = session.get('formdata', None)
        if formdata:
            form = MyForm(MultiDict(formdata))
            form.validate()
            session.pop('formdata')
        return render_template_string(html, form=form)
    
    if form.validate_on_submit():
        # use the form somehow
        # ...
        return redirect('/#registered')

    if form.is_submitted() and not form.validate():
        session['formdata'] = request.form
        return redirect('/#invalid')

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

当你运行服务器时，你会得到:

提交无效表单后，您将被重定向到 /#invalid 并按您的预期填充表单:

• http://flask.pocoo.org/docs/1.0/quickstart/#sessions
• http://flask.pocoo.org/docs/1.0/patterns/flashing/#message-flashing-pattern
• http://flask.pocoo.org/docs/1.0/api/#flask.redirect