We need to work on the speed. This can perhaps help the syntax:
db=DAL()
db.define_table('a',Field('b','integer'))
for i in range(10):
db.a.insert(b=i)
def lazy(f):
def g(self,f=f):
import copy
self=copy.copy(self)
return lambda *a,**b: f(self,*a,**b)
return g
class Scale:
@lazy
def c(self,scale=1):
return self.a.b*scale
db.a.virtualfields.append(Scale())
for row in db(db.a).select():
print row.b, row.c(1), row.c(2), row.c(3)
On Aug 1, 3:10 pm, Michael Toomim <[email protected]> wrote:
> Maybe it helps for me to explain my use-case. I mainly use virtual fields as
> lazy methods, to help traverse related tables. I was actually surprised that
> lazy evaluation wasn't the default. I noticed a few implications of this:
> - Large queries are slowed by virtualfields, even if they won't be needed,
> esp if they query db
> - My definitions for virtualfields aren't as clean as they could be,
> because I have many nested "lazy" funcs in the class definition
> - We can't serialize all objects into session variables
>
> So really I'm just using this because it's a nicer notation to call
> row.otherthing() instead of getotherthing(row). Maybe I really want some
> different feature here?
>
> On Aug 1, 2011, at 5:40 AM, Anthony Bastardi wrote:
>
>
>
>
>
>
>
> > Note, after looking at this some more, Massimo recalled that the reason
> > auth_user virtual fields were excluded from auth.user (and therefore from
> > saving in the session) is because some virtual fields are objects that
> > cannot be pickled and therefore cannot be serialized to store in the
> > session. So, we're thinking of either creating an option to store auth_user
> > virutual fields in auth.user, or maybe testing to make sure the virtual
> > fields can be pickled, and excluding them if not.
>
> > Anthony
>
> > On Mon, Aug 1, 2011 at 5:30 AM, Michael Toomim <[email protected]>
> > wrote:
> > Awesome! I did not know there was an issue submission system.
>
> > On Jul 30, 2011, at 7:02 AM, Anthony wrote:
>
> >> An issue has been submitted, and this should be corrected soon.
>
> >> Anthony
>
> >> On Friday, July 29, 2011 9:57:30 PM UTC-4, Anthony wrote:
> >> auth.user is Storage(table_user._filter_fields(user, id=True)). The
> >> _filter_fields method of the auth_user table only selects actual table
> >> fields, not virtual fields, so auth.user will not include any virtual
> >> fields. Perhaps this should be changed.
>
> >> Anthony
>
> >> On Friday, July 29, 2011 9:05:39 PM UTC-4, Michael Toomim wrote:
> >> I think I found a bug in virtualfields. I have the following
> >> controller:
>
> >> def posts():
> >> user = session.auth.user
> >> n = user.name # returns None
>
> >> Where "person" is defined as a virtualfield on user:
>
> >> class Users():
> >> def name(self):
> >> return self.users.first_name + ' ' + self.users.last_name
> >> db.users.virtualfields.append(Users())
>
> >> The problem is that user.name returns None, because apparently the
> >> virtualfield isn't loaded into the session variable of user.
>
> >> I made this work with the following modification to the controller:
>
> >> def posts():
> >> user = db.users[session.auth.user.id]
> >> n = user.name # returns the user name correctly!
>
> >> I just had to refetch the user from the database.
