Assuming you meant:
r.y.y.y.t
It works because db.a.y is a self referencing field. Inserting into
db.a doesn't return an int, but a Reference, which has a __getattr__
that returns the record it references. Any number of y's should work:
r.y.y.y.y.y.y.y.y.y.y.y.y.y.y.y.y.y.t
't' is the virtual field which returns the length of the computed
field, which in turn is 3*x. 'x' in this case is 'hello', so t is 15.
You could also do:
r.y.y.y.y.z
to get the computed field which should return:
hellohellohello
On Jul 22, 6:50 pm, "mr.freeze" <nat...@freezable.com> wrote:
> It shouldn't. It should throw an error at the print statement because
> 'a' is not defined.
>
> On Jul 22, 6:33 pm, mdipierro <mdipie...@cs.depaul.edu> wrote:
>
> > The following code uses:
> > 1) a computed field
> > 2) a self reference
> > 3) a virtual field
>
> > >>> db.define_table('a',Field('x'),Field('y','reference
> > >>> a'),Field('z',compute=lambda row: row['x']*3))
> > >>> class A:
> > >>> def t(self): return len(self.a.z)
> > >>> db.a.virtualfields.append(A())
> > >>> r=db.a.insert(x='hello')
> > >>> r.update_record(x=r.x,y=r)
> > >>> print a.y.y.y.y.t
>
> > 15
>
> > Can you explain how it works?
