= IS_ONE_OF Validator =

(For large lookup tables use [wiki:IS_ONE_OF_EMPTY IS_ONE_OF_EMPTY])

The '''IS_ONE_OF()''' validator is a custom version of web2py's IS_IN_DB() for foreign key lookups in a key table. In forms, the respective field will be rendered as a drop-down field.

Unlike 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_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 or tuple of field names, 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 (int) to filter for
  - filter_opts=''"options"'' = a list or tuple of allowed values for the filterby-field

  Note:
    - Without represent and if no 'name' field can be detected in the table, the keyfield itself will be used as option label.
    - If filterby is specified, the drop-down fields get sorted by this field.
    - IS_ONE_OF can be cascaded through IS_NULL_OR to include empty selection

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',                          # key table=pr_pentity, key field=id
    shn_pentity_represent,                    # function to represent a pr_pentity entry as string
    filterby='opt_pr_pentity_class',          # type field in the pr_pentity table
    filter_opts=(1,)                          # select only entries with opt_pr_pentity_class in (1,) (select only persons)
    ))
}}}

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DeveloperGuidelines