On Dec 20, 2013, at 8:45 AM, RonnyPfannschmidt <ronny.pfannschm...@gmail.com> wrote:
> 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 != '’))
use:
table.append_constraint(CheckConstraint(parent != '’))
the constraints collection on the Column is handled by the internals.
>
>
> 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>
> 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-unicode
> for something similar (coerces to utf-8, just replace that with checking for
> non-empty).
>
>
>
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