Re: [sqlalchemy] hybrid, relationships and inheritance.
Hi Michael, thanks for your reply. I did get it working with the @property/hybrid_property, but it turns out what I really needed was a custom collection class. At least, that seems to be working in a cleaner fashion. I'm still fumbling around in the dark a little bit, so we'll see how it goes. SQL Alchemy keeps surprising me with features, it's very cool. Cheers, James. Assuming you don't need that (class level behavior), you don't really need @hybrid_property either. You can just use Python's standard @property. If you *did* want that, it would be a little tricky, probably would need a custom comparator. -- 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.
Re: [sqlalchemy] hybrid, relationships and inheritance.
On Jul 7, 2011, at 3:29 PM, James Studdart wrote:
Hi all,
I've got a question regarding hybrid properties and how to use them with
single table inheritance.
I've got a class hierarchy like this (in semi-pseudo code):
class MyBase(object):
# This has the tablename declared attr, id as primary key, generic table
args etc.
class Person(MyBase, Base):
children = relationship('Children')
class SpecialPerson(Person):
partner = relationship('Person')
Okay, so what I want is for SpecialPerson to return both it's own plus it's
partners children. But, if I add to list of children of a special person, it
only adds to it's local children list. Does that make sense?
This is what I've got now, I'm stabbing around in the dark a little bit, so
I'm hoping for some guidance in the correct way to do this with SQL Alchemy.
What you have is fine, though it is only functional at the instance level, that
is:
p = Session.query(SpecialPerson).first()
print p.children
At the class level, the __add__() operator doesn't have any behavior for
relationship() and also cls.partner is again a relationship() which doesn't
have a _children attribute. That is, this wouldn't work:
print
Session.query(SpecialPerson).filter(SpecialPerson.chlidren.contains(some_person))
Assuming you don't need that (class level behavior), you don't really need
@hybrid_property either. You can just use Python's standard @property.
If you *did* want that, it would be a little tricky, probably would need a
custom comparator.
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[sqlalchemy] hybrid, relationships and inheritance.
Hi all,
I've got a question regarding hybrid properties and how to use them
with single table inheritance.
I've got a class hierarchy like this (in semi-pseudo code):
class MyBase(object):
# This has the tablename declared attr, id as primary key, generic
table args etc.
class Person(MyBase, Base):
children = relationship('Children')
class SpecialPerson(Person):
partner = relationship('Person')
Okay, so what I want is for SpecialPerson to return both it's own plus
it's partners children. But, if I add to list of children of a special
person, it only adds to it's local children list. Does that make sense?
This is what I've got now, I'm stabbing around in the dark a little bit,
so I'm hoping for some guidance in the correct way to do this with SQL
Alchemy.
class Person(Mybase, Base):
_children = relationship('Children')
@hybrid_property
def children(self):
return self._children
class SpecialPerson(Person):
partner = relationship('Person')
@hybrid_property
def children(self):
return self._children + self.parter._children
@children.setter
def children(self, value):
self._children = value
Thank you for your time.
Cheers,
James.
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