Flask: AttributeError: 'UnboundField' object has no attribute '__call__'?

问题

Why do I get this error? What is the UnboundField and what do I need to know in order to fix and avoid this problem in the future?

Debug output when I visit http://127.0.0.1:5000/signup:

AttributeError

AttributeError: 'UnboundField' object has no attribute '__call__'
Traceback (most recent call last)

    File "C:\Users\combatmath\Envs\default\lib\site-packages\flask\app.py", line 2000, in __call__

    return self.wsgi_app(environ, start_response)

    File "C:\Users\combatmath\Envs\default\lib\site-packages\flask\app.py", line 1991, in wsgi_app

    response = self.make_response(self.handle_exception(e))

    File "C:\Users\combatmath\Envs\default\lib\site-packages\flask\app.py", line 1567, in handle_exception

    reraise(exc_type, exc_value, tb)

    File "C:\Users\combatmath\Envs\default\lib\site-packages\flask\app.py", line 1988, in wsgi_app

    response = self.full_dispatch_request()

    File "C:\Users\combatmath\Envs\default\lib\site-packages\flask\app.py", line 1641, in full_dispatch_request

    rv = self.handle_user_exception(e)

    File "C:\Users\combatmath\Envs\default\lib\site-packages\flask\app.py", line 1544, in handle_user_exception

    reraise(exc_type, exc_value, tb)

    File "C:\Users\combatmath\Envs\default\lib\site-packages\flask\app.py", line 1639, in full_dispatch_request

    rv = self.dispatch_request()

    File "C:\Users\combatmath\Envs\default\lib\site-packages\flask\app.py", line 1625, in dispatch_request

    return self.view_functions[rule.endpoint](**req.view_args)

    File "C:\Users\combatmath\Apps\ocrbox\routes.py", line 27, in signup

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

    File "C:\Users\combatmath\Envs\default\lib\site-packages\flask\templating.py", line 134, in render_template

    context, ctx.app)

    File "C:\Users\combatmath\Envs\default\lib\site-packages\flask\templating.py", line 116, in _render

    rv = template.render(context)

    File "C:\Users\combatmath\Envs\default\lib\site-packages\jinja2\environment.py", line 989, in render

    return self.environment.handle_exception(exc_info, True)

    File "C:\Users\combatmath\Envs\default\lib\site-packages\jinja2\environment.py", line 754, in handle_exception

    reraise(exc_type, exc_value, tb)

    File "C:\Users\combatmath\Apps\ocrbox\templates\signup.html", line 1, in top-level template code

    {% extends "base.html" %}

    File "C:\Users\combatmath\Apps\ocrbox\templates\base.html", line 9, in top-level template code

    {% block content %}{% endblock %}

    File "C:\Users\combatmath\Apps\ocrbox\templates\signup.html", line 30, in block "content"

    {{ form.submit(class="btn-primary") }}

    AttributeError: 'UnboundField' object has no attribute '__call__'

signup.html:

{% extends "base.html" %}

{% block title %}Join ocrbox!{% endblock %}

{% block content %}
    <main class="container signup-section">
        <div class="section-content">
            <h2>Create an account</h2>

            <form method="POST" action="/signup">


                <div class="form-group">
                    {{ form.first_name.label }}
                    {{ form.first_name }}
                </div>
                <div class="form-group">
                    {{ form.last_name.label }}
                    {{ form.last_name }}
                </div>
                <div class="form-group">
                    {{ form.email.label }}
                    {{ form.email }}
                </div>
                <div class="form-group">
                    {{ form.password.label }}
                    {{ form.password }}
                </div>

                {{ form.submit(class="btn-primary") }}
            </form>
        </div>
    </main>
{% endblock %}

routes.py:

from flask import Flask, render_template, request
from models import db
from forms import SignupForm

app = Flask(__name__)

app.config['SQLALCHEMY_DATABASE_URI'] = 'postgresql://localhost/ocrbox'
db.init_app(app)

app.secret_key = "development-key"

@app.route("/")
def index():
    return render_template("index.html")

@app.route("/about")
def about():
    return render_template("about.html")

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

    if request.method == 'POST':
        return "Success!"
    elif request.method == 'GET':
        return render_template("signup.html", form=form)

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

forms.py:

from flask_wtf import Form
from wtforms import StringField, PasswordField, SubmitField

class SignupForm(Form):
    first_name = StringField('First name')
    last_name = StringField('Last name')
    email = StringField('Email')
    password = PasswordField('Password')
    submit = SubmitField('Sign up')

models.py:

from flask_sqlalchemy import SQLAlchemy
from werkzeug import generate_password_hash, check_password_hash

db = SQLAlchemy()

class User(db.Model):
    __tablename__ = 'users'
    uid = db.Column(db.Integer, primary_key=True)
    firstname = db.Column(db.String(100))
    lastname = db.Column(db.String(100))
    email = db.Column(db.String(120), unique=True)
    pwdhash = db.Column(db.String(54))

    def __init__(self, firstname, lastname, email, password):
        self.firstname = firstname.title()
        self.lastname = lastname.title()
        self.email = email.lower()
        self.set_password(password)

    def set_password(self, password):
        self.pwdhash = generate_password_hash(password)

    def check_password(self, password):
        return check_password_hash(self.pwdhash, password)

回答1:

In routes.py, I think your signup() method should contain form = SignupForm(request.form). Otherwise, form is set to a class instead of an instance.

来源：https://stackoverflow.com/questions/38820081/flask-attributeerror-unboundfield-object-has-no-attribute-call