UNIVERSAL->cando , shortcut for testing and running methods?

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

I love the // operator in perl5.10.

Now

my $home = defined( $args->{home} ) ? $args->{home} : 
         defined($args->{house}) ? $args->{house} :
         confess(q{Can't determine home});
[download]

can be simplified to

my $home = $args->{home} // $args->{house} // confess(q{Can't determin
+e home});
[download]

But if I'm using a super class, is there a shortcut for:

my $home = $self->can('home') ? $self->home : 
        $self->can('house') ? $self->house(1) : 
        confess(q{Can't determine home});
[download]

Something that would let me write it something like this:

my $home = $self->cando('home') // $self->cando('house',1) // confess(
+q{Can't determine home});
[download]

- Boldra

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Re: UNIVERSAL->cando , shortcut for testing and running methods? by ikegami (Patriarch) on Mar 06, 2009 at 07:15 UTC
No need to ~~make up new operators~~add a method to every single class when a sub will do just fine. `sub cando { my $o = shift; my $m = shift; return if !eval { $o->can($m) }; return $o->$m(@_); } my $home = cando($self, 'home') // cando($self, 'house', 1) // confess(q{Can't determine home});` [download] Keep in mind neither your ~~operator~~method nor this sub will work right if `home` returns undef.	[reply] [d/l] [select]
Re: UNIVERSAL->cando , shortcut for testing and running methods? by Rhandom (Curate) on Mar 06, 2009 at 15:14 UTC
Your examples aren't quite parallel. The first one working with hash assignment uses parallel operations. In the second example you pass a different argument to the second subroutine. If you can afford having real parallelism then there is another option available. `my $meth = $self->can('home') \|\| $self->can('house') \|\| confess(q{Can' +t determine home}); my $home = $self->$meth(1);` [download] Which if you were insistent on having be one line could do `my $home = ($self->can('home') \|\| $self->can('house') \|\| confess(q{Can +'t determine home}))->($self, 1);` [download] I think the first is more clear. Yet another option is: `my $meth_name = (grep {$self->can($_)} qw(home house))[0] \|\| confess(q +{Can't determine home}); my $home = $self->$meth_name(1);` [download] However this last option is less optimal in readability and in efficiency. my @a=qw(random brilliant braindead); print $a[rand(@a)];	[reply] [d/l] [select]