In Net::DNS::RR what is the 'can' method?

Lotus1 has asked for the wisdom of the Perl Monks concerning the following question:

This is from the examples section of Net::DNS :

use Net::DNS;
my $res   = Net::DNS::Resolver->new;
my $reply = $res->search("www.example.com", "A");
 
if ($reply) {
    foreach my $rr ($reply->answer) {
        print $rr->address, "\n" if $rr->can("address");
    }
} else {
    warn "query failed: ", $res->errorstring, "\n";
}
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The search method in the resolver returns a packet object. Then the 'answer' method of that (from Net::DNS::Packet) "Returns a list of Net::DNS::RR objects representing the answer section of the packet." I've looked through the documentation for Net::DNS::RR and the module sourch but can't find the description of what the 'can' method is. The example runs without errors while using strict and warnings. Any suggestions?

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Re: In Net::DNS::RR what is the 'can' method? (updated) by haukex (Archbishop) on Sep 19, 2018 at 18:15 UTC
It's ~~probably~~ UNIVERSAL::can. Update: Yep, looks like it. UNIVERSAL is Perl's implicit base class for all objects. `can` queries whether the object has that method (including via inheritance). It looks like the Net::DNS docs are suggesting to use duck typing here to tell whether the Net::DNS::RR subclass has the `address` method. An alternative would be to use `isa` (also from UNIVERSAL) to see if an object is of a certain class (or is one of its subclasses) and therefore supports that class's methods. The thing about that is though that you'd have to test against a whole list of Net::DNS::RR subclasses. As long as all of the subclasses' `address` methods behave the same, duck typing is safe here, and easier.	[reply] [d/l] [select]
Re^2: In Net::DNS::RR what is the 'can' method? by Lotus1 (Vicar) on Sep 19, 2018 at 18:28 UTC
Thanks! I didn't know about that one. Edit: Other examples I've seen just test if the response object is true since it will be 'undef' if there were no responses.	[reply]


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