TypeError:“NoneType”对象不是iterable WTForms字段

Question

下面的代码返回“TypeError”，我认为引起问题的代码部分是 “可用锅炉=数据库会话查询(锅炉.名称).all（）boiler_list=[（b.name）for b in available_boilers]“ 其中boiler list应该被迭代以在表单中形成一个下拉列表。我使用flaskbootstrap快速表单来显示列表，所以我不认为我的问题在那里，为了检查列表是否正在发送，我检查了shell中代码的一部分

@bp.route('/control/addboiler_circuit', methods=('GET', 'POST'))
def addboiler_circuit():
    available_boilers = db.session.query(Boilers.name).all()
    boiler_list = [(b.name) for b in available_boilers]
    form = AddBoiler_CircuitForm()
    form.name.choices = boiler_list
    if form.validate_on_submit():
        boiler_circuits = Boilers_Circuit(name=form.name.data,\
                          BoilerName=form.BoilerName.data)
        db.session.add(boilers_circuits)
        db.session.commit()
        flash('Congratulations, you have now a registered a new boiler 
      circuit!')
        return redirect(url_for('control.addboiler_circuit'))
    return render_template('control/addboiler_circuit.html', title='Add boiler',
                       form=form)

在表单.py在

^{pr2}$

Python壳

>>> available_boilers = db.session.query(Boilers.name).all()
>>> print(available_boilers)
[('Log Burner',), ('solar panel',), ('pellet boiler',)]
>>> boiler_list = [(b.name) for b in available_boilers]
>>> print(boiler_list)
['Log Burner', 'solar panel', 'pellet boiler']

我的代码来自WTForms和{a2}

这对我来说是个新领域，我需要帮助

编辑 下面是完整的错误消息

> Traceback (most recent call last):
1/File "/home/pi/heating/venv/lib/python3.7/site-packages/flask/app.py", 
line 2309, in __call__
return self.wsgi_app(environ, start_response)
2/ File "/home/pi/heating/venv/lib/python3.7/site- 
packages/flask/app.py", 
line 2295, in wsgi_app
response = self.handle_exception(e)
3/ File "/home/pi/heating/venv/lib/python3.7/site-packages/flask/app.py", line 1741, in handle_exception
reraise(exc_type, exc_value, tb)
4/ File "/home/pi/heating/venv/lib/python3.7/site-packages/flask/_compat.py", line 35, in reraise
raise value
5/ File "/home/pi/heating/venv/lib/python3.7/site-packages/flask/app.py", line 2292, in wsgi_app
response = self.full_dispatch_request()
6/ File "/home/pi/heating/venv/lib/python3.7/site-packages/flask/app.py", line 1815, in full_dispatch_request
rv = self.handle_user_exception(e)
7/ File "/home/pi/heating/venv/lib/python3.7/site-packages/flask/app.py", line 1718, in handle_user_exception
reraise(exc_type, exc_value, tb)
8/ File "/home/pi/heating/venv/lib/python3.7/site-packages/flask/_compat.py", line 35, in reraise
raise value
9/ File "/home/pi/heating/venv/lib/python3.7/site-packages/flask/app.py", line 1813, in full_dispatch_request
rv = self.dispatch_request()
10/ File "/home/pi/heating/venv/lib/python3.7/site-packages/flask/app.py", line 1799, in dispatch_request
return self.view_functions[rule.endpoint](**req.view_args)
11/ File "/home/pi/heating/homeHeating/control/control.py", line 49, in addboiler_circuit
form=form)
12/ File "/home/pi/heating/venv/lib/python3.7/site-packages/flask/templating.py", line 135, in render_template
context, ctx.app)
13/ File "/home/pi/heating/venv/lib/python3.7/site-packages/flask/templating.py", line 117, in _render
rv = template.render(context)
14/ File "/home/pi/heating/venv/lib/python3.7/site-packages/jinja2/asyncsupport.py", line 76, in render
return original_render(self, *args, **kwargs)
15/ File "/home/pi/heating/venv/lib/python3.7/site-packages/jinja2/environment.py", line 1008, in render
return self.environment.handle_exception(exc_info, True)
16/ File "/home/pi/heating/venv/lib/python3.7/site-packages/jinja2/environment.py", line 780, in handle_exception
reraise(exc_type, exc_value, tb)
17/ File "/home/pi/heating/venv/lib/python3.7/site-packages/jinja2/_compat.py", line 37, in reraise
raise value.with_traceback(tb)
18/ File "/home/pi/heating/homeHeating/templates/control/addboiler_circuit.html", line 2, in top-level template code
{% import 'bootstrap/wtf.html' as wtf %}
19/ File "/home/pi/heating/homeHeating/templates/base.html", line 1, 
 in top-level template code  {% extends 'bootstrap/base.html' %}
20/ File "/home/pi/heating/venv/lib/python3.7/site- 
  packages/flask_bootstrap/templates/bootstrap/base.html", line 1, in 
top-level template code
{% block doc -%}
21/ File "/home/pi/heating/venv/lib/python3.7/site- 
packages/flask_bootstrap/templates/bootstrap/base.html", line 4, in 
 block "doc"
{%- block html %}
21/ File "/home/pi/heating/venv/lib/python3.7/site- 
packages/flask_bootstrap/templates/bootstrap/base.html", line 20, in 
block 
"html"
 {% block body -%}
22/ File "/home/pi/heating/venv/lib/python3.7/site- 
packages/flask_bootstrap/templates/bootstrap/base.html", line 23, in 
block "body"
{% block content -%} 23/File"/home/pi/heating/homeHeating/templates/control/addboiler_circuit.html", line 8, in block "content" {{ wtf.quick_form(form) }}
24/ File "/home/pi/heating/venv/lib/python3.7/site-packages/jinja2/runtime.py", line 579, in _invoke rv = self._func(*arguments)
25/ File "/home/pi/heating/venv/lib/python3.7/site-packages/flask_bootstrap/templates/bootstrap/wtf.html", line 205, in template {{ form_field(field,
26/ File "/home/pi/heating/venv/lib/python3.7/site-packages/jinja2/runtime.py", line 579, in _invoke rv = self._func(*arguments)
27/ File "/home/pi/heating/venv/lib/python3.7/site-packages/flask_bootstrap/templates/bootstrap/wtf.html", line 123, in template {{field(class="form-control", **kwargs)|safe}}
28/ File "/home/pi/heating/venv/lib/python3.7/site packages/wtforms/fields/core.py", line 155, in __call__ return self.meta.render_field(self, kwargs)
29/ File "/home/pi/heating/venv/lib/python3.7/site packages/wtforms/meta.py", line 56, in render_field return field.widget(field, **render_kw)
30/ File "/home/pi/heating/venv/lib/python3.7/site packages/wtforms/widgets/core.py", line 323, in __call__ for val, label, selected in field.iter_choices():
31/ File "/home/pi/heating/venv/lib/python3.7/site packages/wtforms/fields/core.py", line 454, in iter_choices for value, label in self.choices:
TypeError: 'NoneType' object is not iterable

这是完整的错误脚本，第23行提到了我的表单“addboiler_电路.html“我在下面加了一句：

{% extends "base.html" %}
{% import 'bootstrap/wtf.html' as wtf %}

{% block content %}
    <h1>{{ 'Register' }}</h1>
    <div class="row">
        <div class="col-md-4">
            {{ wtf.quick_form(form) }}
        </div>
    </div>
{% endblock %}

谢谢你看我的问题 敬保罗

编辑30/03/2019 这比我展示的要复杂一点，我最终完成了这个：

@bp.route('/control/addboiler_circuit', methods=('GET', 'POST'))
def addboiler_circuit():
    boiler_list = [(b.id, b.id) for b in db.session.query(Boilers).all()]
    sensorID_list = [(s.id, s.sensorID) for s in db.session.query(Sensors).all()]
    valveID_list = [(p.id, p.name) for p in db.session.query(Pins).all()]
    form = AddBoiler_CircuitForm()
    form.boiler_ID.choices = boiler_list
    form.sensor_ID1.choices = sensorID_list
    form.sensor_ID2.choices = sensorID_list
    form.sensor_ID3.choices = sensorID_list
    form.pin_ID1.choices = valveID_list
    form.pin_ID2.choices = valveID_list
    form.pin_ID3.choices = valveID_list
    if form.validate_on_submit():
        boilercircuits = Boilercircuit(name=form.name.data,\
       boiler_ID=form.boiler_ID.data,sensor_ID1=form.sensor_ID1.data,\
     sensor_ID2=form.sensor_ID2.data,sensor_ID3=form.sensor_ID3.data,\
       pin_ID1=form.pin_ID1.data,pin_ID2=form.pin_ID2.data,\
                   pin_ID3=form.pin_ID3.data)
        db.session.add(boilercircuits)
        db.session.commit()
        flash('Congratulations, you have now a registered a new boiler circuit!')
        return redirect(url_for('control.addboiler_circuit'))
    return render_template('control/addboiler_circuit.html', title='Add boiler',
                       form=form)

现在@sleblanc已经想出了一种全新的方法来编写这个函数，但是我该如何将它放在适当的位置呢？我有很多问题，我不知道从哪里开始。谢谢你的帮助。在

Answer 1

31/ File "/home/pi/heating/venv/lib/python3.7/site packages/wtforms/fields/core.py", line 454, in iter_choices for value, label in self.choices:
TypeError: 'NoneType' object is not iterable

这说明您的表单没有为boilerName字段设置选项。在您的代码中，似乎您正在这样做，但仔细观察后，您是在name字段而不是boilerName字段上设置选项。在

你的代码也有其他问题。Choices应该是(id, 'label')元组的列表。如果您的模型引用了一个文本字符串，那么您可以简单地执行[(b.name, b.name) for b in available_boilers]。在

另外，由于您使用的是flask_wtf，因此您应该以这种方式重写您的视图以使其更清楚：

^{pr2}$

此外，考虑使用WTForms SQLAlchemy的queryselect字段来填充选项，这样可以节省更多样板文件：

from wtforms_sqlalchemy.fields import QuerySelectField

class AddBoiler_CircuitForm(FlaskForm):
    name = StringField('Name', validators=[DataRequired()])
    boiler = QuerySelectField(
                'Boiler name', 
                query_factory=lambda: Boiler.query.all(),
                validators=[DataRequired()])

通过在电路模型上设置一个名为“锅炉”的关系，表单的populate_obj将完全按照您期望的方式进行。QuerySelectField甚至可以确保用户的选择包含在您提供的查询中，从而防止狡猾的用户编辑HTML表单和提交不允许的值。在