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Re: See if a certain package has a certain sub, without executing that sub

by gmax (Abbot)
on Mar 20, 2004 at 15:27 UTC ( #338300=note: print w/replies, xml ) Need Help??


in reply to See if a certain package has a certain sub, without executing that sub

Use the can method (it's a method of the UNIVERSAL package, so every class in Perl has access to it).

#!/usr/bin/perl use strict; use warnings; package Communications; sub SendMessage { my $packages = shift; my $msg = shift; for (@$packages) { if ($_->can('ReceiveMessage') ) { $_->ReceiveMessage($msg); } else { print "$_ can't ReceiveMessage\n" } } } sub ReceiveMessage { print __PACKAGE__, "::ReceiveMessage('$_[1]')\n"; } package Second; sub ReceiveMessage { print __PACKAGE__, "::ReceiveMessage('$_[1]')\n"; } package Other; sub nothing { print "\n"; } package main; my @packages = qw(Communications Other Second); Communications::SendMessage( \@packages, 'hello'); __END__ output: Communications::ReceiveMessage('hello') Other can't ReceiveMessage Second::ReceiveMessage('hello')
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Re: Re: See if a certain package has a certain sub, without executing that sub
by muba (Priest) on Mar 20, 2004 at 15:33 UTC
    Wow! This one is great! It's also nice to read:
    "if it can receive message" :)
    Thank you a lot!

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[atcroft]: james28909: What about October 5, 1582?
[stevieb]: atcroft: "Make both hands into fists..."... is something my Ma taught me in our native lang, but I was to ignorant and young to pay attention. Thanks for that :)
[atcroft]: stevieb: Sad to say that I only recently learned that particular trick, but I have since found it very useful.... :)
[james28909]: ill be back with a solution eventually
[stevieb]: it's a reminder to re-inforce it :P
[atcroft]: james28909: That particular questions was a bit of trick, actually (depending on the country you are in). More interesting is, if you are trying to subtract from an epoch time, for instance, you might have to consider when/if DST occurs for a location,
[atcroft]: because you may have to adjust the number of seconds you change from an epoch from 86400 (not to mention leap seconds)....
[atcroft]: james28909: Although if your program is using a database, you might be able to "pass the buck" to the database and ask it to do the date change for you....

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