Mohith Mohith - 1 month ago 9
Perl Question

Perl: elegant way to check if something is object blessed as package?

I want to check if a

$thing
is an object blessed as a package (e.g.
__PACKAGE__
). One idea is:

use Scalar::Util qw(blessed);

defined blessed $thing && blessed $thing eq __PACKAGE__


Is there a better and/or more elegant way that avoids checking if the return value of
blessed
is defined?

Another approach is
(blessed $thing or '') eq __PACKAGE__
, but I'm not sure if a package can legally be empty or not.

Also, based on Perl Monks,
UNIVERSAL::isa($thing, __PACKAGE__)
is another way, but that approach is permissive of more things.

Answer

You can use the predefined ref function:

ref($thing) eq __PACKAGE__

That said, I think the more-permissive isa is really better practice. You shouldn't generally need to check if an object's type is exactly something.

[…] I'm not sure if a package can legally be empty or not.

It cannot. (And incidentally, if you try to bless a reference to '', it will actually get blessed into main. Perl will warn you about this, provided you have -w or use warnings.)