麻煩與QuerySelectField在燒瓶WTF

Question

我想擁有一個充滿燒瓶形式的SQLAlchemy的請求的結果選擇字段，但我不斷收到一個「類型錯誤：‘NoneType’對象不是可迭代

我（how to use QuerySelectField in flask?），但它並沒有幫助我解決爲什麼我的查詢（選擇= Course.query.all（））回來沒有問題 - 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格式：

{% 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

致盲明顯的閃光：

我的助手功能沒有產生回報.....

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