I'm trying to simplify a terribly complicated network inventory program by using objects, but I can't figure out how to do what I want to do.

Given a list of pingable IP addresses, I use async SNMP to query sysName, sysDesc, and sysObjectID. This part is easy.

But here's where I get stuck. Given the IP addresses that reply to the SNMP query, I want to create an SNMPDevice object. However, in the constructor of SMNPDevice, I want to do some additional queries to see if the device requires special handling (like a cisco switch stack where one IP address actually consists of multiple hardware units). If a special device type is detected, I want the SNMPDevice object to create an object of the appropriate derived class (like SNMPDevice::CiscoStack) and returning it instead of its own blessed self.

Something like this: 

package SMNPDevice;

sub new {
   my $class = shift;
   my $ip = shift;
   my $sysName = shift;
   my $sysDesc = shift;
   my $sysObjectID = shift;

   my @members = GetStackMembers($ip);
   return SNMPObject::CiscoStack::new($ip, $sysName, $sysDesc, $sysObj
+ectID) if scalar @members > 1;

   return SNMPDevice::CiscoWLC::new($ip, $sysName, $sysDesc, $sysObjec
+tID) if $sysDesc =~ /Cisco WLC/;

   #etc
}

[download]
Or, would SNMPDevice bless itself as a SNMPDevice::CiscoStack ?

In reply to Can a class constructor create an instance of a derived class and return it? Or, can objects transmute into other objects? by poodad

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