I'm sorry, that was a doofus comment. Of course lambdas allow side-
effects! I wish mailing lists supported "delete."
On Aug 27, 1:08 pm, Michael Toomim <too...@gmail.com> wrote:
> Interesting approach to use lambdas. Since lambdas don't do side-
> effects, I checked out my virtualfields to see if my uses have side
> effects.
>
> In my app I have:
> 12 methods total across 3 database tables
> 10 of those methods have no side-effects
> 2 have side-effects
>
> The two methods with side-effects are:
> 1. row.delete() ... deletes the relevant rows in related tables
> 2. row.toggle_x() ... toggles the boolean field of x and updates
> cached data on other tables and sends email notifications
>
> Perhaps this information is useful in designing the next lazy
> virtualfields.
>
> On Aug 25, 9:14 pm, Massimo Di Pierro <massimo.dipie...@gmail.com>
> wrote:
>
>
>
>
>
>
>
> > We are moving away from this because of many problems. Try this
> > instead. It is still experimental but may go into stable soon.
>
> > def vfields():
> > db.define_table('item',
> > Field('unit_price','double'),
> > Field('quantity','integer'))
> > db(db.item.id>0).delete()
>
> > db.item.lazy_total_price=Field.lazy(lambda
> > self:self.item.unit_price*self.item.quantity)
>
> > db.item.bulk_insert([{'unit_price':12.00, 'quantity': 15},
> > {'unit_price':10.00, 'quantity': 99},
> > {'unit_price':120.00, 'quantity': 2},])
> > res = []
> > for r in db(db.item.id>0).select():
> > res.append([r.unit_price, r.quantity, r.lazy_total_price()])
> > return dict(res=res)
>
> > On Aug 25, 7:50 am, Martin Weissenboeck <mweis...@gmail.com> wrote:
>
> > > I wanted to learn more about lazy virtual fields and therefore I have
> > > repeated the example from the book:
>
> > > def vfields():
> > > db.define_table('item',
> > > Field('unit_price','double'),
> > > Field('quantity','integer'))
>
> > > db(db.item.id>0).delete()
>
> > > class MyVirtualFields:
> > > def lazy_total_price(self):
> > > return lambda self=self: self.item.unit_price*self.item.quantity
>
> > > db.item.virtualfields.append (MyVirtualFields())
>
> > > db.item.bulk_insert([{'unit_price':12.00, 'quantity': 15},
> > > {'unit_price':10.00, 'quantity': 99},
> > > {'unit_price':120.00, 'quantity': 2},])
>
> > > res = []
> > > for r in db(db.item.id>0).select():
> > > res.append([r.unit_price, r.quantity, r.lazy_total_price()])
> > > return dict(res=res)
>
> > > The expected output is:
> > > [[12.0, 15, 180.0], [10.0, 99, 990.0], [120.0, 2, 240.0]]
>
> > > But I got
> > > * [[12.0, 15, *240.0]*, [10.0, 99, *240.0*], [120.0, 2, 240.0]]*
> > > *
> > > *
> > > *Three times the same result.
> > > *
> > > I have read the book and my program over and over again - but I cannot see
> > > any error.*
> > > *
>
> > > Does somebody have an idea?
> > > Martin
