I think I need to generate value of that field before commit, some how.
On Friday, May 23, 2014 10:55:31 AM UTC+4, Pavel Aborilov wrote:
>
> 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 <abor...@gmail.com> 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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