You right, I dont have "name" column in "commands" table, thats why If I do
def __init__(self, **kw):
kw.setdefault(“name”, “Command”)
super(Command, self).__init__(**kw)
name = column_property(Column(String(50), default=“Command”),
DB_Object.name)
I have: "table commands has no column named".
I dont need this column in "Command", but in "Command" I need to set "name"
of "DB_Object" to value that depends on other "Command" columns.
How can I do this?
On Friday, May 23, 2014 12:51:14 AM UTC+4, Michael Bayer wrote:
>
>
> On May 22, 2014, at 7:42 AM, Pavel Aborilov <[email protected]<javascript:>>
> 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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