The example works wonderfully,
however i noticed, that when i attach a constraint to the column, it gets
mirrored in the table
so the event handler
@event.listens_for(PString, "after_parent_attach")
def create_constraint(target, parent):
@event.listens_for(parent, "after_parent_attach")
def add_to_table(col, table):
col.constraints.add(CheckConstraint(parent != ''))
will result in
CREATE TABLE fun (
name VARCHAR(100) CHECK (name != ''),
CHECK (name != '')
)
instead of
CREATE TABLE fun (
name VARCHAR(100) CHECK (name != '')
)
when using
m = MetaData()
t = Table(
'fun', m,
Column('name', PString(100)),
)
e = create_engine('sqlite://', echo=1)
m.create_all(e)
m.drop_all(e)
assert 0
On Wednesday, December 18, 2013 5:26:53 PM UTC+1, Michael Bayer wrote:
>
>
> On Dec 18, 2013, at 5:41 AM, RonnyPfannschmidt
> <ronny.pfa...@gmail.com<javascript:>>
> wrote:
>
> > Hi,
> >
> > for supporting a certain schema requirement,
> > i have to create a quite a number of columns that are checked not to be
> a empty string,
> >
> > So i'd like to declare a custom type, which will automatically imply the
> check on those columns.
> >
> > I already Investigated, how Boolean does this for databases with
> non-native boolean types,
> > however it uses number "private" methods,
> >
> > Should i follow its example or is there a official way?
> >
> > what i currently have to do is
> >
> > Column('foo', String(20), CheckConstraint("foo <> ''")
> >
> > what i'd like use is something like
> >
> > Column('foo', PString(20))
>
> you’d use a TypeDecorator for this. See the example
> http://docs.sqlalchemy.org/en/rel_0_9/core/types.html#coercing-encoded-strings-to-unicodefor
> something similar (coerces to utf-8, just replace that with checking
> for non-empty).
>
>
>
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