NAME

       Set::NestedGroups - grouped data eg ACL's, city/state/country etc

SYNOPSIS

         use Set::NestedGroups;
         $nested = new Set::NestedGroups;
         $nested->add('user','group');
         $nested->add('group','parentgroup');
         do_something() if($nested->member('user','parentgroup'));

DESCRIPTION

       Set::NestedGroups gives an implementation of nested groups, access control lists (ACLs)
       would be one example of nested groups.

       For example, if Joe is a Manager, and Managers have access to payroll, you can create an
       ACL which implements these rules, then ask the ACL if Joe has access to payroll.

       Another example, you may wish to track which city, state and country people are in, by
       adding people to cities, cities to states, and states to countries.

CONSTRUTORS

       new()
           creates a new Set::NestedGroups object.

       new( fh )
           creates a new Set::NestedGroups object, the object will be initialized using data read
           from this handle. For details on the format, see the save() method

       new( $sth )
           creates a new Set::NestedGroups object, the object will be initialized using data read
           using this this DBI statement handle.  For details on the format, see the save()
           method

METHODS

       add ( $member, $group)
           adds a member to a group. The group will be created if it doesn't already exist.

       remove ( $member, $group )
           removes a member from a group. If this was the last member in this group, then the
           group will be deleted. If the member was only in this group, then the member will be
           deleted.

       save(FILEHANDLE)
           Outputs the object to the given filehandle, which must be already open in write mode.

           The format is compatible with the format used by CGI, and can be used with new to
           initialize a new object;

           Returns true if successfully wrote the data, or false if something went wrong (usually
           that meant that the handle wasn't already open in write mode).

       save($sth)
           Saves the object to a DBI database. This can be used with new to initialize a new
           object. The $sth should be expecting 2 values, in this fashion:

             $sth = $dbh->prepare('insert into acl values (?,?)')
             $acl->save($dbh);
             $sth->finish();

             $sth = $dbh->prepare('select * from acl');
             $newacl=new ACL($sth);

           Returns true if successfully wrote the data, or false if something went wrong.

       member ( $member, $group )
           Returns true if $member is a member of $group.

       member ( $member )
           returns true if $member exists in any group.

       group ( $group )
           returns true if $group exists

       groups ( $member, %options )
           Returns the groups that $member belongs to. Options are explained below.

       members ( $group , %options )
           Returns the members of $group. Keep on reading for the options

       list(%options)
           Returns a Set::NestedGroups::Member object that will output an list of the members &
           groups. This could be considered a calling of groups() on each member, except this is
           more efficient.

           The object can be used as follows.

             $list=$nested->list();
             for(my $i=0;$i<$list->rows();$i++){
               my ($member,$group)=$list->next();
               print "$member=$group\n";
             }

   options
       By default, the above methods give every valid combination. However you might not always
       want that. Therefore there are options which can prevent return of certain values.

       All of these examples presume that 'joe' is a member of 'managers', and 'managers' is a
       member of payroll, and that you are using only one of these options. You can use all 3,
       but that gets complicated to explain.

       -norecurse=>1

       No Recursion is performed, method would ignore payroll, and return only managers.

       -nomiddles=>1

       Doesn't returns groups 'in the middle', method would ignore mangers, and return only
       payroll.

       -nogroups=>1

       Doesn't return members that are groups. This only applies to the list() method, in which
       case it acts like nomiddles, except on the member instead of the group. list would ignore
       managers and return joe => managers , joe => payroll.

       This sounds a lot more confusing than it actually is, once you try it once or twice you'll
       get the idea.

AUTHOR

       Alan R. Barclay, gorilla@elaine.drink.com

SEE ALSO

       perl(1), CGI, DBI.

POD ERRORS

       Hey! The above document had some coding errors, which are explained below:

       Around line 276:
           You forgot a '=back' before '=head1'

       Around line 278:
           '=item' outside of any '=over'

       Around line 350:
           You forgot a '=back' before '=head2'

       Around line 378:
           =back doesn't take any parameters, but you said =back 2

           =back without =over