16 Jun 2003 03:08:51 UTC
- Distribution: Acme-Holy
- Module version: 0.03
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Acme::Holy - Test whether references are blessed.
use Acme::Holy; my $ref = ... some reference ... my $obj = bless $ref , 'Some::Class'; print holy( $obj ); # prints 'Some::Class' print ( holy  ? 'object' : 'not object' ); # prints 'not object'
This module is a classic case of reinventing the wheel and not enough RTFM. Unless you really like having terms such as
holyin your code, you should use the official "holy" implementation now found in the Perl core: Scalar::Util. There you will find the
blessedfunction which behaves identically to
... Oh well, on with the show ...
Acme::Holy provides a single routine, holy(), which returns the name of the package an object has been
blessed into, or
undef, if its first argument is not a blessed reference.
Isn't this what
ref()does already? Yes, and no. If given a blessed reference,
ref()will return the name of the package the reference has been blessed into. However, if
ref()is passed an unblessed reference, then it will return the type of reference (e.g.
CODEREF, etc). This means that a call to
ref()by itself cannot determine if a given reference is an object. holy() differs from
undefif its first argument is not a blessed reference (even if it is a reference).
Can't we use
UNIVERSAL::isa()? Yes, and no. If you already have an object, then
isa()will let you know if it inherits from a given class. But what do we do if we know nothing of the inheritance tree of the object's class? Also, if we don't have an object, just a normal reference, then attempting to call
isa()through it will result in a run-time error.
holy() is a quick, single test to determine if a given scalar represents an object (i.e. a blessed reference).
By default, Acme::Holy exports the method holy() into the current namespace. Aliases for holy() (see below) may be imported upon request.
- holy scalar
holy() accepts a single scalar as its argument, and, if that scalar is a blessed reference, returns the name of the package the reference has been blessed into. Otherwise, holy() returns
To reflect that there are many terms for referring to something that is blessed, Acme::Holy offers a list of aliases for holy() that may be imported upon request:
use Acme::Holy qw( blessed );
The following aliases are supported:
The idea for this module came from a conversation I had with David Cantrell <firstname.lastname@example.org>. However, the lack of RTFM is a clear failing on my part. It was obviously a good idea, otherwise someone wouldn't have already written it.
Ian Brayshaw, <email@example.com>
Copyright 2003 by Ian Brayshaw
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.