如何在具有可读显示下拉列表的模型中显示烧瓶外键字段？答案

【问题标题】：How to show flask foreign key field in modelform with readable display dropdown?如何在具有可读显示下拉列表的模型中显示烧瓶外键字段？
【发布时间】：2020-05-14 23:04:45
【问题描述】：

我的模型中有一对多和多对多的关系。我正在使用wtforms_alchemy ModelForm 创建表单，但ForeignKey 字段没有显示为下拉字段，它也将整数显示为其中的值。我尝试引用类似的问题并尝试了答案，例如，我将__str__() 和__repr__() 函数放入其中，以便它们在下拉列表中返回一些可读且有意义的字符串，但这并没有发生。有谁知道我还能怎么做？

Models.py-


class Product(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(20), nullable=False)
    location_id = db.Column(db.Integer, db.ForeignKey('location.id'))

    def __init__(self, name, location=None):
        self.name = name
        if location:
            self.location_id = location.id

    def __repr__(self):
        warehouse = Location.query.filter_by(id = self.location_id).first()
        qty = warehouse.get_product_quantity(self.name)
        return '{0}-{1}-{2}'.format(self.name, warehouse.name, qty)

class Location(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(20), unique=True, nullable=False)
    products = db.relationship('Product', backref='warehouse')

    def __init__(self, name):
        self.name = name

    def __repr__(self):
        return 'Location-{0}'.format(self.name)

class Movement(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    timestamp = db.Column(db.DateTime, nullable=False, default=datetime.utcnow)
    from_location_id = db.Column(db.Integer, db.ForeignKey("location.id"))
    to_location_id = db.Column(db.Integer, db.ForeignKey("location.id"))
    from_location = db.relationship(Location, lazy='joined', foreign_keys=[from_location_id], backref='from_location')
    to_location = db.relationship(Location, lazy='joined', foreign_keys=[to_location_id], backref='to_location')
    product_id = db.Column(db.Integer, db.ForeignKey('product.id'))
    product = db.relationship(Product, backref='movements')
    qty = db.Column(db.Integer)

forms.py -

class ProductForm(ModelForm, Form):
    class Meta:
        model = Product
        include = ['name']

class LocationForm(ModelForm, Form):
    class Meta:
        model = Location
        include = ['name']

class MovementForm(ModelForm, Form):
    class Meta:
        model = Movement
        include = ['from_location_id', 'to_location_id', 'product_id', 'qty']

【问题讨论】：

标签： foreign-keys flask-sqlalchemy dropdown flask-wtforms modelform

【解决方案1】：

你需要从你的路由函数中传递选择选项

使用模型和表单的示例：

@app.route('/movement/<movement_id>')
def edit_movement(movement_id):
    products = db.engine.execute("select id, product_name from products")
    form.product.choices = [(p.id, p.product_name) for p in products]
    return render_template('movement.html', movement_id=movement_id, form=form)

【讨论】：

【解决方案2】：

由于 ID 是整数，WTForm-ALchemy 会将表单字段转换为整数字段，您可以看到 here

因此，您可以按照here 的说明强制使用选择字段

如果您想要更多可读性，可以使用QuerySelectField。

class MovementForm(ModelForm, Form):
    class Meta:
        model = Movement

    product = QuerySelectField(
        query_factory=lambda: Product.query.all(),
        get_pk=lambda a: a.id,
        get_label=lambda a: a.name,
        allow_blank=False,
    )

如果您愿意，可以使用视图/路由来查询并将选项传递给表单。

def movement_new():
    movement = Movement()
    form = MovementForm(obj=movement)

    products = [(c.id, c.name) for c in Product.query.all()]
    form.product_id.choices = products
    ...

然后在 MovementForm 上

class MovementForm(ModelForm, Form):
    class Meta:
        model = Movement    ---> note tha the include was removed

    product_id = SelectField('Product', coerce=int)
  ...

【讨论】：