= IS_ONE_OF Validator =

The IS_ONE_OF() validator is a custom version of web2py's IS_IN_DB() for foreign key lookups in a key table. Other than IS_IN_DB, the IS_ONE_OF validator is deletion status sensitive, i.e. records in the key table that are flagged as 'deleted' will be ignored.

Furthermore, it is possible to filter the key records by a type field (which should be int) for certain options

Usage:
  db.table.field.requires = IS_NULL_OR(IS_ONE_OF(db, ''"keytable.keyfield"'', ''represent'', filterby=''"fieldname"'', filter_opts=''options''))

  - ''keytable'' = Name of the key table
  - ''keyfield'' = Name of the key field
  - ''represent'' = how to build the option label (in drop-downs in forms) from the key entry, one of the following:
    - string template, e.g. "%(first_name)s %(last_name)s"
    - list of names of fields, e.g. ('first_name', 'last_name')
    - function or lambda, e.g. lambda r: "%(first_name)s %(last_name)s" % dict(r)
  - filterby=''"fieldname"'' = the type field (and int-field) to filter for
  - filter_opts=''"options"'' = a list or tuple of allowed values for the filterby-field

  If filterby is specified, the drop-down fields get sorted by this field.

Example:
{{{
...
db.Field('pr_pe_id', db.pr_pentity),
...

db[table].pr_pe_id.requires = IS_NULL_OR(IS_ONE_OF(db,
    'pr_pentity.id',
    shn_pentity_represent,
    filterby='opt_pr_pentity_class',
    filter_opts=(1,)
    ))
}}}