[sqlalchemy] sqlalchemy.exc.InvalidRequestError: Mapper properties (i.e. deferred,column_property(), relationship(), etc.) must be declared as @declared_attr callables on declarative mixin classes.
Hi,
I currently have the following mix-in class construction (based on the
documentation
http://docs.sqlalchemy.org/en/latest/orm/extensions/declarative/mixins.html
)
Base = declarative_base()
class BaseCountry(object):
""" Managed through Kotti """
@declared_attr
def __tablename__(cls):
return cls.__name__.lower()
dpis_id = Column(Integer, primary_key=True)
title = Column(Unicode(80))
regions = relationship("Region",
primaryjoin="Country.dpis_id==Region.country_id")
class Country(BaseCountry, Base):
""" Managed through Kotti """
__tablename__ = 'countries'
This gives me
File
"/data/home/ajung/src/kotti/lib/python2.7/site-packages/sqlalchemy/ext/declarative/api.py",
line 55, in __init__
_as_declarative(cls, classname, cls.__dict__)
File
"/data/home/ajung/src/kotti/lib/python2.7/site-packages/sqlalchemy/ext/declarative/base.py",
line 88, in _as_declarative
_MapperConfig.setup_mapping(cls, classname, dict_)
File
"/data/home/ajung/src/kotti/lib/python2.7/site-packages/sqlalchemy/ext/declarative/base.py",
line 103, in setup_mapping
cfg_cls(cls_, classname, dict_)
File
"/data/home/ajung/src/kotti/lib/python2.7/site-packages/sqlalchemy/ext/declarative/base.py",
line 123, in __init__
self._scan_attributes()
File
"/data/home/ajung/src/kotti/lib/python2.7/site-packages/sqlalchemy/ext/declarative/base.py",
line 216, in _scan_attributes
"Mapper properties (i.e. deferred,"
sqlalchemy.exc.InvalidRequestError: Mapper properties (i.e.
deferred,column_property(), relationship(), etc.) must be declared as
@declared_attr callables on declarative mixin
classes.
Where is the difference to the documentation?
Python 2.7, Sqlalchemy 1.0.11
Andreas
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Re: [sqlalchemy] sqlalchemy.exc.InvalidRequestError: Mapper properties (i.e. deferred,column_property(), relationship(), etc.) must be declared as @declared_attr callables on declarative mixin classes
Hi Andreas,
On Fri, Jan 15, 2016 at 02:56:39AM -0800, Andreas Jung wrote:
> Hi,
>
> I currently have the following mix-in class construction (based on the
> documentation
> http://docs.sqlalchemy.org/en/latest/orm/extensions/declarative/mixins.html
> )
>
> Base = declarative_base()
>
> class BaseCountry(object):
>""" Managed through Kotti """
>
>@declared_attr
>def __tablename__(cls):
>return cls.__name__.lower()
>
>dpis_id = Column(Integer, primary_key=True)
>title = Column(Unicode(80))
>regions = relationship("Region",
> primaryjoin="Country.dpis_id==Region.country_id")
As the error message in the exception says, this attribute needs to be
declared as a declared_attr, like this:
@declared_attr
def regions(cls):
return relationship("Region",
primaryjoin="Country.dpis_id==Region.country_id")
This is stated in the following section of the docs:
http://docs.sqlalchemy.org/en/latest/orm/extensions/declarative/mixins.html#mixing-in-relationships
Good luck,
Michal
>"Mapper properties (i.e. deferred,"
> sqlalchemy.exc.InvalidRequestError: Mapper properties (i.e.
> deferred,column_property(), relationship(), etc.) must be declared as
> @declared_attr callables on declarative mixin
> classes.
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Re: [sqlalchemy] sqlalchemy.exc.InvalidRequestError: Mapper properties (i.e. deferred,column_property(), relationship(), etc.) must be declared as @declared_attr callables on declarative mixin classes
On Fri, Jan 15, 2016 at 02:26:37PM +0100, Michal Petrucha wrote:
> Hi Andreas,
>
> On Fri, Jan 15, 2016 at 02:56:39AM -0800, Andreas Jung wrote:
> > Hi,
> >
> > I currently have the following mix-in class construction (based on the
> > documentation
> > http://docs.sqlalchemy.org/en/latest/orm/extensions/declarative/mixins.html
> > )
> >
> > Base = declarative_base()
> >
> > class BaseCountry(object):
> >""" Managed through Kotti """
> >
> >@declared_attr
> >def __tablename__(cls):
> >return cls.__name__.lower()
> >
> >dpis_id = Column(Integer, primary_key=True)
> >title = Column(Unicode(80))
> >regions = relationship("Region",
> >
> > primaryjoin="Country.dpis_id==Region.country_id")
>
> As the error message in the exception says, this attribute needs to be
> declared as a declared_attr, like this:
>
> @declared_attr
> def regions(cls):
> return relationship("Region",
> primaryjoin="Country.dpis_id==Region.country_id")
...and just after I sent the email I realized this wouldn't work
either, because it hardcodes a fixed string as the originating table
name. Something like the following should work, though (according to
the docs I linked):
@declared_attr
def regions(cls):
return relationship("Region",
primaryjoin=lambda: cls.dpis_id == Region.country_id
)
...or perhaps this one, if you prefer:
@declared_attr
def regions(cls):
return relationship("Region",
primaryjoin="%s.dpis_id==Region.country_id" % cls.__name__
)
> This is stated in the following section of the docs:
> http://docs.sqlalchemy.org/en/latest/orm/extensions/declarative/mixins.html#mixing-in-relationships
>
> Good luck,
>
> Michal
>
> >"Mapper properties (i.e. deferred,"
> > sqlalchemy.exc.InvalidRequestError: Mapper properties (i.e.
> > deferred,column_property(), relationship(), etc.) must be declared as
> > @declared_attr callables on declarative mixin
> > classes.
>
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