What you are saying makes perfect sense. Thank you for showing me the
light. The code below incorporates what I think you were saying and
allows me to still test it easily. Thanks again. A+++ for the
SQLAlchemy community!!!
class SA_Model(Base):
__tablename__ = 'test0'
id = Column(Integer, primary_key=True)
title = Column(String)
def __init__(self, title):
self.title=title
class Model():
def __init__(self, *args):
self.session=Session()
if type(args[0])==int:
self.instance=self.session.query(SA_Model).get(args[0])
elif type(args[0])==str:
self.instance = SA_Model(args[0])
def commit(self):
self.session.add(self.instance)
self.session.commit()
model1=Model('test1')
model1.commit()
id=model1.instance.id
del model1
model2=Model(id)
model2.instance.title='text2'
model2.commit()
On Jan 15, 8:49 pm, "Jackson, Cameron"
<[email protected]> wrote:
> 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=
>
> > --
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