Flask-WTF中的QuerySelectField造成問題

Question

我正在嘗試將一個選擇字段填充為燒瓶形式的sqlalchemy請求的結果，但是我不斷收到“ TypeError：'NoneType'對象是不可迭代的

我已經看過這個答案（ 如何在燒瓶中使用QuerySelectField？ ），但這並不能幫助我解決為什么我的查詢（choices = Course.query.all（））什么都沒回來的問題-我認為這是問題。

我的models.py：

class Course(db.Model):
    __tablename__ = 'courses'
    id = db.Column(db.Integer, primary_key=True)
    course_name = db.Column(db.String, nullable=False)
    course_description = db.Column(db.String, nullable=True)
    course_location = db.Column(db.String, nullable=True)
    start_date = db.Column(db.DateTime, nullable=True)
    end_date = db.Column(db.DateTime, nullable=True)
    start_time = db.Column(db.Time, nullable=True)
    end_time = db.Column(db.Time, nullable=True)
    max_number_students = db.Column(db.Integer, default=8)
    spaces_left = db.Column(db.Integer, default=5)
    is_active = db.Column(db.Boolean, default=True)
    price = db.Column(db.Float, nullable=True)



    def __init__(self, course_name=None, course_description=None, course_location=None,start_date=None,end_date=None,
                start_time=None,end_time=None,max_number_students=None,spaces_left=None,is_active=None, price=None):
        self.course_name = course_name
        self.course_description=course_description
        self.course_location = course_location
        self.start_date = start_date
        self.end_date = end_date
        self.start_time = start_time
        self.end_time = end_time
        self.max_number_students = max_number_students
        self.spaces_left = spaces_left
        self.is_active = is_active
        self.price = price


    def __repr__(self):
        return "<course name {}>".format(self.course_name)


class Purchase(db.Model):
    __tablename__ = 'purchases'
    uuid = db.Column(db.String, primary_key=True)
    email = db.Column(db.String)
    product_id = db.Column(db.Integer, db.ForeignKey('courses.id'))
    payment_method = db.Column(db.String, nullable=True, default="Credit Card")
    notes = db.Column(db.String, nullable=True)
    date_purchased = db.Column(db.DateTime, nullable=False, default=func.now())
    product = db.relationship(Course)

    def __init__(self, uuid,email=None, product_id=None, product=None,payment_method=None, notes=None, date_purchased=None):
        self.uuid=uuid
        self.email=email
        self.product_id=product_id
        self.product = product
        self.payment_method=payment_method
        self.notes=notes
        self.date_purchased=date_purchased

我的forms.py

from flask_wtf import Form
from wtforms.ext.sqlalchemy.fields import QuerySelectField
from wtforms import StringField,
from wtforms.validators import DataRequired, Length, Email, 
from project.models import Course

def select_group():
        choices = Course.query.all()
        form = EnrollmentForm(obj=choices)
        form.product.choices = [(c.id, c.course_name) for c in choices]

class EnrollmentForm(Form):

    email = StringField(
        "email",
        validators=[DataRequired(), Email(message = None),Length(min=3, max=40)]
    )
    product= QuerySelectField(query_factory=select_group)
    payment_method = StringField('Payment', validators=[DataRequired()])
    notes = StringField('Notes', validators=[DataRequired()])

和html形式：

{% block content %}
      <h1>register</h1>
      <br>
      <form class="form-signin" action = ""  method = "post">
        {{ form.csrf_token }}

        <div>{{ form.email.label }}: {{ form.email() }}</div>
        <div>{{ form.product.label }}: {{ form.product() }}</div>
        <div>{{ form.payment_method.label }}: {{ form.payment_method() }}</div>
        <div>{{ form.notes.label }}: {{ form.notes() }}</div>



      <button class="btn btn-sm btn-success" type="submit">Sign in</button>
     </form>


     {% endblock %}

Answer 1

明顯的致盲閃光：

我的輔助函數沒有產生回報.....

def select_group():
        return Course.query.all()