[web2py] IS_IN_DB no dropdown list

[Rage Callao]

hi,

i'm just starting to learn web2py and i'm worndering what i'm doing wrong
here:

my db.py contains:

import datetime
now=datetime.date.today()

db=SQLDB('mysql://cookbook:cookbook@127.0.0.1/cookbook')

db.define_table('category',
                Field('name',length=32))

db.define_table('recipe',
                Field('title',length=32),
                Field('description',length=256),
                Field('category',db.category),
                Field('date','date',default=now),
                Field('instructions','text'))

db.category.name.requires=[IS_NOT_EMPTY(),IS_NOT_IN_DB(db,'category.name')]
db.recipe.title.requires=[IS_NOT_EMPTY()]
db.recipe.description.requires=[IS_NOT_EMPTY()]
db.recipe.category.requires=[IS_IN_DB(db, db.category.id, db.category.name)]
db.recipe.date.requires=[IS_DATE()]

but i'm not getting a dropdown box in the category field as supposed to.

any help?