in reply to Re: Report on Blessing to 'tag' an object
in thread Report on Blessing to 'tag' an object

If necessary you could use UNIVERSAL::isa() to check if the blessed ref is an array ref:

isa won't always work:

my $o = bless {}, 'ARRAY';
print "$o isa array" if UNIVERSAL::isa($o, 'ARRAY');

__END__
ARRAY=HASH(0x759c) isa array

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When you want to know your implementation type you want reftype from Scalar::Util.

use Scalar::Util qw(reftype);

my $hash_object = bless {}, 'ARRAY';
my $array_ref = [1,2,3];
my $array_object = bless [], 'Foo';

foreach ($hash_object, $array_ref, $array_object) {
    print "reftype of ", $_, " is ", reftype($_), "\n";
};

__END__
reftype of ARRAY=HASH(0x759c) is HASH
reftype of ARRAY(0x7650) is ARRAY
reftype of Foo=ARRAY(0x74b8) is ARRAY

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Re^3: Report on Blessing to 'tag' an object
by tye (Sage) on Jan 21, 2003 at 16:44 UTC

    That won't always work:     Can't locate Scalar/Util.pm in @INC Which do you think is more likely? 1) That I blessed a non-array reference into the package named 'ARRAY' and I'll be upset that UNIVERSAL::isa() gets confused or 2) That I don't have Scalar::Util ?

    I think Scalar::Util has become "core" and so in a few years, the probabilities will shift. For now, I much prefer UNIVERSAL::isa() because I like my code to work on relatively old versions of Perl and I don't mind that it is possible to break my code by doing extremely stupid things. q-:

                    - tye
[reply]
[d/l]

      Fair point :-)

      Scalar::Util has been core since 5.007003 for those interested.

      Personally, I prefer catch the weird cases - even if I have to install a few modules to do so.

[reply]
        This particular module should be useful without other (non-core) dependancies, and should run on Perl 5.6. There is another place Scalar::Util would come in handy (to distinguish a floating-point literal from a string literal), but I'm trying to do without.

        I thought about using isa rather than ref, but figured the latter is faster and I know exactly what the possibilities are. That is, I won't see a derived class coming back in.

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