问题描述
我正在学习Flask-SQLAlchemy教程.我在python 2.6上有Flask 0.9,sqlalchemy 0.7.8和flask-sqlalchemy 0.16.
I'm following the Flask-SQLAlchemy tutorial.I have Flask 0.9, sqlalchemy 0.7.8 and flask-sqlalchemy 0.16 on python 2.6.
我正在尝试建立一对多"的关系,就像在他们的教程中一样.
I'm trying to create a "one to many" relationship, like in their tutorial.
class Person(db.Model):
id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.String(50))
addresses = db.relationship('Address', backref='person',
lazy='dynamic')
class Address(db.Model):
id = db.Column(db.Integer, primary_key=True)
email = db.Column(db.String(50))
person_id = db.Column(db.Integer, db.ForeignKey('person.id'))
之后,我可以创建数据库:
After that, I can create the database :
from DataBase.Tables.MyClass import db
db.create_all()
当两个类都在同一文件上创建时,效果很好.
It works well when both classes are created on the same file.
当我想通过2个不同的文件(2个不同的模块)创建此文件时,它将不再起作用.
It does not work anymore when I want to create this through 2 different files (2 different modules).
这只是一个例子(我正在尝试使用很多类来做更复杂的事情,我需要在2个不同的模块之间存在这种关系,但是我会简化它,所以我的问题是会更容易理解.)
This is just an example (I'm trying to do something much more complicated with plenty of classes and I need the relationship to exist between 2 different modules but I'll simplify it so my question can be easier to understand.)
我有2个模块:人"和地址",两个都有:
I have 2 modules : Person and Address, both of them have :
app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///C:\\MyBase\\Base.sqlite'
db = SQLAlchemy(app)
并且每个人都有之前编写的类的声明.
and each of them has the declaration of the class written before.
我的主要功能在第三个模块中:
My main function is in a 3rd module:
from DataBase.Tables.Person import db as person_db
from DataBase.Tables.Address import db as address_db
if __name__ == "__main__":
import DataBase.Tables.Person
import DataBase.Tables.Address
person_db.create_all()
address_db.create_all()
在Eclipse中我仍然出现错误:
I still get an error in Eclipse:
* sqlalchemy.exc.NoReferencedTableError:与列"Address.person_id"相关联的外键找不到表"person",通过该表可生成目标列"sid"的外键*
*sqlalchemy.exc.NoReferencedTableError: Foreign key associated with column 'Address.person_id' could not find table 'person' with which to generate a foreign key to target column 'sid'*
我可以找到另一条有人建议使用元数据"的帖子,但我找不到合适的使用方式.
I could find another post with someone suggesting the use of "metadata" but I couldn't find a proper way to use that.
有人有解决这个问题的想法吗?
Does anyone have an idea to solve this ?
谢谢!
推荐答案
您只需拥有以下一组,而不必为每个模型单独准备一份副本:
You need to have only one set of the below, and not a separate copy for each model:
app = Flask(my_app_name)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///C:\\MyBase\\Base.sqlite'
db = SQLAlchemy(app)
这可以在单独的模块中定义(将其称为shared
),并导入到每个模型定义文件中.
在这种情况下,主模块将更像:
This can be defined in a separate module (lets call it shared
), and imported into each model definition file.
In this case the main module will look more like:
from DataBase.Tables.shared import db
if __name__ == "__main__":
import DataBase.Tables.Person # will load Person model into the db
import DataBase.Tables.Address # will load Address model into the db
db.create_all() # will create all models
这篇关于Flask Sqlalchemy:不同模块之间的关系的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!