Re: [sqlalchemy] mixing association proxies and mixin classes
That works like a charm, thanks!
On 06/21/2012 12:46 AM, Michael Bayer wrote:
do it like this for now:
class FilterMixin(object):
@declared_attr
def _filters(cls):
cls.filters = association_proxy('_filters', 'filter')
return relationship(cls.filter_class,
cascade='all,delete,delete-orphan')
there's a patch for 0.8 only in http://www.sqlalchemy.org/trac/ticket/2517 .
On Jun 20, 2012, at 1:13 PM, Wichert Akkerman wrote:
I am struggling a little bit with mixin classes. The pattern I am trying to
implement is a mixin-class that adds a list of validated search queries to a
model. A minimised version of the code is below. The problem I am running into
is that putting an association_proxy on a mixin class does not appear to work
here: it always picks the first seen class type to create new values instead of
picking up what the relationship of the current instance requires. With the
example below that results in this error:
AssertionError: Attribute '_filters' on class 'class '__main__.TypeB'' doesn't
handle objects of type'class '__main__.FilterA''
My initial though was that this might be fixed by making the association_proxy
instance itself a declared_attr, but that results in other problems.
Is there an alternative way to implement this, or is this a bug in the
declarative logic?
from sqlalchemy import *
from sqlalchemy.orm import *
from sqlalchemy.ext.associationproxy import association_proxy
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.ext.declarative import declared_attr
metadata = MetaData()
BaseObject = declarative_base(metadata=metadata)
class BaseFilter(BaseObject):
__abstract__ = True
id = Column(Integer(), primary_key=True, autoincrement=True)
filter = Column(UnicodeText(), nullable=False)
@declared_attr
def __tablename__(cls):
return '%s_filter' % cls.parent_tablename
@declared_attr
def parent_id(cls):
return Column(Integer(),
ForeignKey('%s.id' % cls.parent_tablename,
ondelete='CASCADE', onupdate='CASCADE'),
nullable=False, index=True)
def __init__(self, filter, **kw):
super(BaseFilter, self).__init__(filter=filter, **kw)
@validates('filter')
def validate_filter(self, key, value):
assert len(value) 2
return value
class FilterA(BaseFilter):
parent_tablename = 'type_a'
class FilterB(BaseFilter):
parent_tablename = 'type_b'
class FilterMixin(object):
@declared_attr
def _filters(cls):
return relationship(cls.filter_class,
cascade='all,delete,delete-orphan')
filters = association_proxy('_filters', 'filter')
#@declared_attr
#def filters(cls):
#return association_proxy('_filters', 'filter')
class TypeA(BaseObject, FilterMixin):
__tablename__ = 'type_a'
filter_class = FilterA
id = Column(Integer(), primary_key=True, autoincrement=True)
class TypeB(BaseObject, FilterMixin):
__tablename__ = 'type_b'
filter_class = FilterB
id = Column(Integer(), primary_key=True, autoincrement=True)
engine = create_engine('sqlite://')
metadata.bind = engine
metadata.create_all()
Session = sessionmaker(bind=engine)
session = Session()
session.add(TypeA(filters=[u'foo']))
session.add(TypeB(filters=[u'foo']))
session.flush()
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[sqlalchemy] mixing association proxies and mixin classes
I am struggling a little bit with mixin classes. The pattern I am trying
to implement is a mixin-class that adds a list of validated search
queries to a model. A minimised version of the code is below. The
problem I am running into is that putting an association_proxy on a
mixin class does not appear to work here: it always picks the first seen
class type to create new values instead of picking up what the
relationship of the current instance requires. With the example below
that results in this error:
AssertionError: Attribute '_filters' on class 'class '__main__.TypeB'' doesn't
handle objects of type'class '__main__.FilterA''
My initial though was that this might be fixed by making the
association_proxy instance itself a declared_attr, but that results in
other problems.
Is there an alternative way to implement this, or is this a bug in the
declarative logic?
from sqlalchemy import *
from sqlalchemy.orm import *
from sqlalchemy.ext.associationproxy import association_proxy
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.ext.declarative import declared_attr
metadata = MetaData()
BaseObject = declarative_base(metadata=metadata)
class BaseFilter(BaseObject):
__abstract__ = True
id = Column(Integer(), primary_key=True, autoincrement=True)
filter = Column(UnicodeText(), nullable=False)
@declared_attr
def __tablename__(cls):
return '%s_filter' % cls.parent_tablename
@declared_attr
def parent_id(cls):
return Column(Integer(),
ForeignKey('%s.id' % cls.parent_tablename,
ondelete='CASCADE', onupdate='CASCADE'),
nullable=False, index=True)
def __init__(self, filter, **kw):
super(BaseFilter, self).__init__(filter=filter, **kw)
@validates('filter')
def validate_filter(self, key, value):
assert len(value) 2
return value
class FilterA(BaseFilter):
parent_tablename = 'type_a'
class FilterB(BaseFilter):
parent_tablename = 'type_b'
class FilterMixin(object):
@declared_attr
def _filters(cls):
return relationship(cls.filter_class,
cascade='all,delete,delete-orphan')
filters = association_proxy('_filters', 'filter')
#@declared_attr
#def filters(cls):
#return association_proxy('_filters', 'filter')
class TypeA(BaseObject, FilterMixin):
__tablename__ = 'type_a'
filter_class = FilterA
id = Column(Integer(), primary_key=True, autoincrement=True)
class TypeB(BaseObject, FilterMixin):
__tablename__ = 'type_b'
filter_class = FilterB
id = Column(Integer(), primary_key=True, autoincrement=True)
engine = create_engine('sqlite://')
metadata.bind = engine
metadata.create_all()
Session = sessionmaker(bind=engine)
session = Session()
session.add(TypeA(filters=[u'foo']))
session.add(TypeB(filters=[u'foo']))
session.flush()
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Re: [sqlalchemy] mixing association proxies and mixin classes
do it like this for now:
class FilterMixin(object):
@declared_attr
def _filters(cls):
cls.filters = association_proxy('_filters', 'filter')
return relationship(cls.filter_class,
cascade='all,delete,delete-orphan')
there's a patch for 0.8 only in http://www.sqlalchemy.org/trac/ticket/2517 .
On Jun 20, 2012, at 1:13 PM, Wichert Akkerman wrote:
I am struggling a little bit with mixin classes. The pattern I am trying to
implement is a mixin-class that adds a list of validated search queries to a
model. A minimised version of the code is below. The problem I am running
into is that putting an association_proxy on a mixin class does not appear to
work here: it always picks the first seen class type to create new values
instead of picking up what the relationship of the current instance requires.
With the example below that results in this error:
AssertionError: Attribute '_filters' on class 'class '__main__.TypeB''
doesn't handle objects of type'class '__main__.FilterA''
My initial though was that this might be fixed by making the
association_proxy instance itself a declared_attr, but that results in other
problems.
Is there an alternative way to implement this, or is this a bug in the
declarative logic?
from sqlalchemy import *
from sqlalchemy.orm import *
from sqlalchemy.ext.associationproxy import association_proxy
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.ext.declarative import declared_attr
metadata = MetaData()
BaseObject = declarative_base(metadata=metadata)
class BaseFilter(BaseObject):
__abstract__ = True
id = Column(Integer(), primary_key=True, autoincrement=True)
filter = Column(UnicodeText(), nullable=False)
@declared_attr
def __tablename__(cls):
return '%s_filter' % cls.parent_tablename
@declared_attr
def parent_id(cls):
return Column(Integer(),
ForeignKey('%s.id' % cls.parent_tablename,
ondelete='CASCADE', onupdate='CASCADE'),
nullable=False, index=True)
def __init__(self, filter, **kw):
super(BaseFilter, self).__init__(filter=filter, **kw)
@validates('filter')
def validate_filter(self, key, value):
assert len(value) 2
return value
class FilterA(BaseFilter):
parent_tablename = 'type_a'
class FilterB(BaseFilter):
parent_tablename = 'type_b'
class FilterMixin(object):
@declared_attr
def _filters(cls):
return relationship(cls.filter_class,
cascade='all,delete,delete-orphan')
filters = association_proxy('_filters', 'filter')
#@declared_attr
#def filters(cls):
#return association_proxy('_filters', 'filter')
class TypeA(BaseObject, FilterMixin):
__tablename__ = 'type_a'
filter_class = FilterA
id = Column(Integer(), primary_key=True, autoincrement=True)
class TypeB(BaseObject, FilterMixin):
__tablename__ = 'type_b'
filter_class = FilterB
id = Column(Integer(), primary_key=True, autoincrement=True)
engine = create_engine('sqlite://')
metadata.bind = engine
metadata.create_all()
Session = sessionmaker(bind=engine)
session = Session()
session.add(TypeA(filters=[u'foo']))
session.add(TypeB(filters=[u'foo']))
session.flush()
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