There are two distinctions here. First:
Field('owner', db.person)
is equivalent to:
Field('owner', 'reference person')
However, the latter is generally preferred because if you are using lazy
table definitions, the former method triggers the full definition of
db.person, so you lose the benefit of the lazy definition.
Second:
db.dog.owner.requires = IS_IN_DB(db, 'person.id', '%(name)s')
is equivalent to:
Field('owner', 'reference person', requires=IS_IN_DB(db, 'person.id',
'%(name)s'))
Again, though, the latter is preferable in the case of lazy tables because
the former will trigger the full db.dog table definition. Of course, as
Massimo pointed out, neither of the above are really necessary if you
specify the "format" argument in the db.person table definition, as that
will result in a default validator equivalent to the above.
Anthony
On Friday, August 30, 2013 12:51:41 AM UTC-7, Mirko wrote:
>
> Hi all,
> I am really new to web2py and I find this python framework really exciting.
>
> I am currently reading the whole online book chapter database validators,
> and while I was reading at the example given, I was wondering if there is a
> difference between this :
>
> db.define_table('person', Field('name', unique=True))
> db.define_table('dog', Field('name'), Field('owner', db.person))
> db.dog.owner.requires = IS_IN_DB(db, 'person.id', '%(name)s')
>
> and this :
>
> db.define_table('person', Field('name', unique=True), format='%(name)s')
> db.define_table('dog', Field('name'), Field('owner', type='reference
> person', required=True))
>
> Thanks a lot,
>
> Mirko
>
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