In the MVC architecture, the application class I mentioned is your controller, and the session is part of it.
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Jackson, Cameron Sent: Monday, 16 January 2012 12:45 PM To: [email protected] Subject: RE: [sqlalchemy] Re: Initialize model by its primary key. You are correct that an object should initialise itself, but don't take that to mean that Test0 should be responsible for every use case where a Test0 is going to be created. If you need some logic that says, for example, 'If a Test0 already exists with id x, then return it, otherwise create a new Test0 with id x', then that kind of comparison and object creation should be managed outside the class. The philosophy behind this is that any given Test0 instance shouldn't really have too much control or knowledge of anything outside of its own internal values. Let some other object (your own application class) maintain the collection of objects in memory, and another object again (the session) control the flow of data to/from the database. Sorry, I'm not sure if I'm being clear here or if I'm rambling a bit. Does any of that make sense to you? -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of gpitel Sent: Monday, 16 January 2012 12:27 PM To: sqlalchemy Subject: [sqlalchemy] Re: Initialize model by its primary key. Thanks for the quick response. I am not a programmer by trade, so your insight is a great help. My program is split up into a model, a view, and a controller. I have been validating my model using unit testing ( from what I have read testing the controller and view is debatable). The reason I have a session inside the model, is because initialization sometimes depends on the existing table -> query -> session. Model initialization should ( I thought) remain on the model side, so one could easily test the model. Bayer's link/recipe was scary for a noob like me, so I may have not other choice but to move session outside of the model. I will post my example when I get it working. ~Grant On Jan 15, 6:42 pm, "Jackson, Cameron" <[email protected]> wrote: > Putting a session inside a model seems like an odd thing to want to do. > Changes in session A won't show up in session B until you commit() A and > rollback() B (which of course will destroy changes you may have made in B). > > I think your Test0 constructor should just be: > > def __init__(self, title=''); > self.title = title > > And then you can move the other logic out of the model: > class MyApplication(object): > > def __init__(self): > self.session = Session() > > def GetOrCreateTest0(id): > test0 = self.session.query(Test0).filter_by(id=id).first(): > if not test0: > test0 = Test0() > self.session.add(test0) > return test0 > > I may have misunderstood exactly what you were trying to accomplish, but does > that help? > > > > > > > > -----Original Message----- > From: [email protected] [mailto:[email protected]] On > Behalf Of gpitel > Sent: Sunday, 15 January 2012 11:46 PM > To: sqlalchemy > Subject: [sqlalchemy] Initialize model by its primary key. > > I am trying to setup my model initialization in two different ways. > 1.) Initialize normally by creating an instance, e.g., > test0=Test0('Title') > 2.) Initialize by query, using an input integer as the primary key, > e.g., test0=Test(32) > > This posses two questions. Is it common practice to put a session > inside the model? Google Code search seems to say no, but I don't see > any other option. When I query inside the model, the attributes show > up inside the class but not outside of it. How do I fix this? I have > included some example code and output. > > Thanks for your help. > > ~Grant > > == CODE == > > class Test0(Base): > __tablename__ = 'test0' > id = Column(Integer, primary_key=True) > title = Column(String) > session=Session() > def __init__(self, *args): > if type(args[0])==int: > test=self.session.query(Test0).get(args[0]) > self=self.session.merge(test) > self.session.add(self) > elif type(args[0])==str: > self.title=args[0] > self.session.add(self) > def commit(self): > self.session.commit() > > test0a=Test0('This is a test.') > test0a.commit() > test0b=Test0(test0a.id) > print 'test0a title=' + str(test0a.title) > print 'test0b title=' + str(test0b.title) > test0b.title='CHANGED' > test0b.commit() > > == OUTPUT == > test0a title=This is a test. > test0b title=None= > > -- > You received this message because you are subscribed to the Google Groups > "sqlalchemy" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]. > For more options, visit this group > athttp://groups.google.com/group/sqlalchemy?hl=en. > > ------------------------------------------------------------------------- > DISCLAIMER: This e-mail transmission and any documents, files and > previous e-mail messages attached to it are private and confidential. > They may contain proprietary or copyright material or information that > is subject to legal professional privilege. 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