SQLAlchemy的瓶 - 與兩個以上的列

Question

我創建一個購物車，爲了這個，我現在用的是以下車型在瓶關聯表：

line_item = db.Table('line_item', 
        db.Column('cart_id', db.Integer, db.ForeignKey('cart.id')), 
        db.Column('product_id', db.Integer, db.ForeignKey('product.id')), 
        db.Column('price', db.Float) 
        ) 


class Cart(db.Model): 
    id = db.Column(db.Integer, primary_key=True) 


class Product(db.Model): 
    id = db.Column(db.Integer, primary_key=True) 
    title = db.Column(db.Unicode(64), index=True, unique=True) 
    description = db.Column(db.Unicode(500), index=True, unique=True) 
    image_url = db.Column(db.Unicode(128)) 
    price = db.Column(db.Float) 
    line_item = db.relationship('Cart', secondary=line_item, backref=db.backref('products', lazy='dynamic')) 

我想在關聯表使用一個額外的列「 line_item「包含價格，以便在用戶將其添加到購物車時節省產品的價格。

我知道沒有price列我會做以下操作來添加這些數據。

p = Product() 
c = Cart() 
p.line_item.append(c) 
db.session.add(p) 
db.session.commit() 

我該如何在關聯表中插入price？

Answer 1

使用db.Model您LineItem - 未經測試的代碼如下：

class LineItem(db.Model): 
    __tablename__ = 'line_items'   
    cart_id = db.Column(db.Integer, db.ForeignKey('carts.id'), primary_key=True) 
    product_id = db.Column(db.Integer, db.ForeignKey('products.id'), primary_key=True) 
    price = db.Column(db.Float)  
    cart = db.relationship("Cart", back_populates="line_items") 
    product = db.relationship("Product", back_populates="carts") 


class Cart(db.Model): 
    __tablename__ = 'carts' 
    id = db.Column(db.Integer, primary_key=True) 
    line_items = db.relationship(LineItem, back_populates="cart")  


class Product(db.Model): 
    __tablename__ = 'products' 
    id = db.Column(db.Integer, primary_key=True) 
    title = db.Column(db.Unicode(64), index=True, unique=True) 
    description = db.Column(db.Unicode(500), index=True, unique=True) 
    image_url = db.Column(db.Unicode(128)) 
    price = db.Column(db.Float) 
    carts = db.relationship(LineItem, back_populates="product")  


p = Product() 
c = Cart() 

line_item = LineItem() 
line_item.price = p.price 
line_item.product = p 

c.line_items.append(line_item)