Hi all,
I want to know if I am using SQLAlchemy in a correct and proper way for Many
to One Relations between objects and database tables. I have created a test
case for Cars and Brands. Each car can have a name and one Brand. I wonder if
I use the setter in the Car Class correctly and if the assignement in the car
mapper is correct also.
Just to be clear, it is working, but I want to know if I use everything
correctly here.
Many thanks for your comments
Frank
CODE:
#!/usr/bin/python
# coding: utf-8
from sqlalchemy import create_engine, Table, Column, Integer, String,
MetaData, ForeignKey
from sqlalchemy.orm import mapper, sessionmaker, relation, backref
engine = create_engine('sqlite:///:memory:', echo=True)
class Car(object):
def __init__(self, name):
self.name = name
self.brand = None
self.brand_id = None
def setBrand(self, brand):
self.brand_id = brand.id
self.brand = brand
class Brand(object):
def __init__(self, name):
self.name = name
metadata = MetaData()
brands = Table('brands', metadata
,Column('id', Integer, primary_key=True)
,Column('name', String(10),
nullable=False))
cars = Table('cars', metadata
,Column('id', Integer, primary_key=True)
,Column('name', String(10),
nullable=False)
,Column('brand_id', Integer,
ForeignKey('brands.id')))
metadata.create_all(engine)
mapper(Car, cars, properties={'brand': relation(Brand)})
mapper(Brand, brands)
Session = sessionmaker(bind=engine, autoflush=True)
ps = Session()
porsche = Brand('Porsche')
bmw = Brand('BMW')
audi = Brand('Audi')
# some Audis
a4 = Car('A4 quattro')
a4.setBrand(audi)
a6 = Car('A6')
a6.setBrand(audi)
# a BMW
i326 = Car('i326')
i326.setBrand(bmw)
ps.add(a4)
ps.add(a6)
ps.add(i326)
res = ps.query(Car)
for a_car in res:
print a_car.brand.name
--
Frank Broniewski
Metrico s.àr.l. ( http://www.metrico.lu )
36, rue des Romains
L-5433 Niederdonven
Luxembourg
Fon: +352 26 74 94 28
Fax: +352 26 74 94 99
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