On Tue, Jan 27, 2009 at 6:02 PM, Ross Vandegrift <[email protected]> wrote:
> class Book(object):
> def __init__(self, title, author):
> self.title = title
> self.author = author
> self.bookmark = None
>
> def bookmark(self, pageno):
> self.bookmark = pageno
Any normal methods you define in this class will operate on a single
book record, and it should probably not access the Session directly.
If you want a method that operates on multiple records, you can use a
class method:
@classmethod
def get_all(class_):
q = meta.Session.query(class_).filter_by(user_id=1)
return q.all()
books = model.Book.get_all()
However, I would return the query object rather than a list, so that
the controller or template can call any of its methods it wants (.all,
.count, etc). That provides a nice generic API for all these
operations. However, by exposing the query, you're also tying the
controller/template to SQLAlchemy. This only matters if you think you
might switch to another database system later.
Creating objects I normally do directly in the controller, and same
for deleting or modifying. However, you could make class methods for
these too. Or functions in the model.
You can also make a base class with common methods for your ORM
classes. One of my applications has this in the meta module:
class ORMClass(object):
"""Base class for all ORM classes."""
_id_attribute = None
@classmethod
def query(class_):
return Session.query(class_)
@classmethod
def get(class_, id):
return class_.query().get(id)
def __repr__(self):
if self._id_attribute:
value = getattr(self, self._id_attribute)
if isinstance(value, basestring):
id_str = " '%s'" % value
elif isinstance(value, (int, long)):
id_str = " #%s" % value
elif value is None:
id_str = " ''"
else:
id_str = " %s" % value
else:
id_str = ""
return "<%s%s>" % (self.__class__.__name__, id_str)
But sometimes I wonder whether such trivial magic as .query and .get
is worth it.
--
Mike Orr <[email protected]>
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