Hi, I am wondering if there is a way to completely decouple the association proxy declaration from my Python classes, and contain this to a database class? My goal is not to 'burden' developers looking at the main part of my code with SQLAlchemy when there is no need to directly interact with the database. This in order to heighten the readability/extendability of my code. All the examples I have seen thus far declare the association proxy directly within the class definition, which I would like to avoid.
Below I have attached a piece of generalized code to which I would like to apply this principle (let's hope the indentation survives the email...). In reality the class declarations would be located within a different file and imported in the database class to decouple these sections of the code. In case your wondering: the goal of the code is a self-referential n-n relation where the association class has an extra attribute which needs to be accessible from inside the program. Most code has been borrowed from the broker/stocks example[1]. Any ideas? Or is this simply not possible at this time? This is my first encounter with SQLAlchemy, and perhaps I have missed the obvious somehow... Regards, Arn Vollebregt [1] http://www.sqlalchemy.org/docs/05/reference/ext/associationproxy.html#building-complex-views <test.py> from sqlalchemy import create_engine, MetaData, Table, Column, Integer, String, ForeignKey from sqlalchemy.orm import sessionmaker, mapper, relation from sqlalchemy.ext.associationproxy import association_proxy from sqlalchemy.orm.collections import attribute_mapped_collection engine = create_engine('sqlite:///test.db', echo=True) metadata = MetaData() Session = sessionmaker(bind=engine) session = Session() def createAssociationObject(otherMyObject, myProperty): return AssociationObject(otherMyObject=otherMyObject, myProperty=myProperty) class MyObject(object): myObjects = association_proxy('myPropertyProxy', 'myProperty', creator=createAssociationObject) def __init__(self, name): self.name = name def __str__(self): # potential infinit recursion #return "<myObject(name=%s, myObjects=%s)>" % (self.name, self.myObjects) return "<myObject(name=%s, #myObjects=%i)>" % (self.name, len (self.myObjects)) def __repr__(self): return self.__str__() class AssociationObject(object): def __init__(self, myObject=None, otherMyObject=None, myProperty=0): self.myObject = myObject self.otherMyObject = otherMyObject self.myProperty = myProperty myObjectsTable = Table("myObjects", metadata, Column('id', Integer, primary_key=True), Column('name', String(25), nullable=False), ) AssociationObjectsTable = Table("associationObjects", metadata, Column('myObjectID', Integer, ForeignKey('myObjects.id'), primary_key=True), Column('otherMyObjectID', Integer, ForeignKey('myObjects.id'), primary_key=True), Column('myProperty', Integer), ) mapper(MyObject, myObjectsTable, properties={ 'myPropertyProxy': relation(AssociationObject, collection_class=attribute_mapped_collection('myProperty'), primaryjoin=AssociationObjectsTable.c.myObjectID==myObjectsTable.c.id,) }) mapper(AssociationObject, AssociationObjectsTable, properties={ 'myObject': relation(MyObject, primaryjoin=AssociationObjectsTable.c.myObjectID==myObjectsTable.c.id,), 'otherMyObject': relation(MyObject, primaryjoin=AssociationObjectsTable.c.otherMyObjectID==myObjectsTable.c.id,) }) metadata.create_all(engine) myObject1 = MyObject('testObject1') myObject2 = MyObject('testObject2') myObject3 = MyObject('testObject3') myObject1.myObjects[myObject2] = 1 myObject2.myObjects[myObject1] = 1 myObject3.myObjects[myObject2] = 1 myObject3.myObjects[myObject1] = 2 session.add(myObject1) session.add(myObject2) session.add(myObject3) session.commit() for myObject in session.query(MyObject).order_by(MyObject.id): print myObject for otherMyObject, myProperty in myObject.myObjects.items(): print "\t" + str(otherMyObject), str(myProperty) </test.py> --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to sqlalchemy@googlegroups.com To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~----------~----~----~----~------~----~------~--~---
