On May 22, 2014, at 7:42 AM, Pavel Aborilov <[email protected]> wrote:
> Hi!
> How can I set default for parent field?
>
> class DB_Object(Base):
> __tablename__ = 'objects'
> id = Column(Integer, primary_key=True)
> name = Column(String(50), unique=True, nullable=False)
> type = Column(String(50))
> __mapper_args__ = { 'polymorphic_identity': 'object', 'polymorphic_on':
> type }
>
> class Command(DB_Object):
> __tablename__ = "commands"
> id = Column(Integer, ForeignKey('objects.id'), primary_key=True)
> name = Column(String(50), default="Command")
>
> If I try to commit Command object
> I have "objects.name may not be NULL"
This is all assuming that "name" is the same value on both DB_Object and on
Command.
Since Command extends from DB_Object, you'd want to remove the "name "column
from the "commands" table - it is redundant vs. the "name" column that's on
"objects".
Alternatively, you can map both "name" columns on Command as follows:
class Command(DB_Object):
# ...
name = column_property(Column(String(50), default="Command"), DB_Object.name)
However, in either case, you will also need to establish that "default" value
in the constructor (or in the init event, see
http://docs.sqlalchemy.org/en/latest/orm/events.html?highlight=init%20event#sqlalchemy.orm.events.InstanceEvents.init)
, so that it applies to both "name" columns during flush:
class Command(DB_Object):
# ...
def __init__(self, **kw):
kw.setdefault("name", "Command")
super(Command, self).__init__(**kw)
>
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