Question

在我的应用程序中，一个“ 设置”可以与多个“ 产品”相关联。针对一组列出的产品必须定义数量。对于这种多对多关系，我遵循SQLAlchemy documentation使用带有附加列（quantity）的关联表。

使用下面包含的代码，我能够使用Flask-WTF生成的表单成功更新表中的现有（手动输入）数据，但无法添加新的“关联”。我收到以下错误：

TypeError: populate_obj: cannot find a value to populate from the 
provided obj or input data/defaults

我怀疑是因为python无法定位/没有set_id的值。当我print(form.data)时，我看到以下输出：

'products': [{'product_id': 1, 'quantity': '105', 'csrf_token': '...'}, {'product_id': 2, 'quantity': '123', 'csrf_token': '...'}, {'product_id': 4, 'quantity': '120', 'csrf_token': '..'}]

您是否同意可能缺少对set.id的引用？我尝试在主表单类set.id中包含一个SetForm()字段，但这没有用。是否可以通过某种方式将其传递给populate_obj()还是应该通过像这样遍历表单数据来“手动”完成？

for item in form.products.entries:
   product = Product.query.filter_by(id=item.data['product_id'])
   set = Set.query.get(id)
   association = Set_Product_Association(set=set, product=product, quantity=data['quantity']
   db.session.add(association)

（希望是）相关的代码位：

forms.py

class SetProdForm(FlaskForm):
    product_id = SelectField('Product', coerce=int)
    quantity = TextField()

    def __init__(self, *args, **kwargs):
        super(SetProdForm, self).__init__(*args, **kwargs)
        self.product_id.choices = [(product_id.id, product_id.part_number)
                                 for product_id in Product.query.order_by(Product.part_number).all()]

class SetForm(FlaskForm):
    ...
    products = FieldList(FormField(SetProdForm), min_entries=3)
    submit = SubmitField('Update')

models.py

class Set_Product_Association(db.Model):
    __tablename__ = 'set_product_association'

    set_id = db.Column(db.Integer, db.ForeignKey('sets.id'), primary_key=True)
    product_id = db.Column(db.Integer, db.ForeignKey('products.id'), primary_key=True)

    quantity = db.Column(db.Integer)

    product = db.relationship("Product", back_populates="sets")
    set = db.relationship("Set", back_populates="products")

class Set(db.Model):
    __tablename__ = 'sets'

    id = db.Column(db.Integer, primary_key=True)
    products = db.relationship("Set_Product_Association", 
                                        back_populates="set")

class Product(db.Model):
    __tablename__= 'products'

    id = db.Column(db.Integer, primary_key=True)
    part_number = db.Column(db.String(100), unique=True, nullable=False)
    sets = db.relationship("Set_Product_Association", 
                                     back_populates="product")

views.py

@main.route('/sets/edit/<int:id>',  methods = ['GET', 'POST'])
@login_required
def editSet(id):
     setToBeEdited = Set.query.get_or_404(id)
     form = SetForm(obj=setToBeEdited)
     if form.validate_on_submit():
        form.populate_obj(setToBeEdited)
        db.session.add(setToBeEdited)
        db.session.commit()
        flash('Set definition has been updated.')
        return redirect(url_for('.sets'))
     return render_template('edit_set.html', form=form)

使用WTForms populate_obj用多余的列更新多对多关联表

0 个答案: