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Class::BlackHole(3) User Contributed Perl Documentation Class::BlackHole(3)

Class::BlackHole - base class to treat unhandled method calls as no-ops

  use Class::BlackHole;

  # set up a class X, to inherit from Class::BlackHole
  @X::ISA = qw(Class::BlackHole);
  # put a method in it
  sub X::zaz { 123123; }
  print "Zaz is <", X->zaz, ">\n";
  print "Flork is <", X->flork, ">\n";
  print "can zaz : <", X->can('zaz'), ">\n";
  print "can flork : <", X->can('flork'), ">\n";
  The above code prints:
   Zaz is <123123>
   Flork is <>
   can zaz : <CODE(0x392c7d4)>
   can flork : <>

Normally, if you try to call a method that there's no handler for, you get an error:

  Can't locate object method "flork" via package "X".

But for classes that inherit from Class::BlackHole, unhandled methods become just no-operations.

Be sure to have Class::BlackHole be the absolute last item in your class's ISA list.

This class will almost definitely not work right as part of any ISA tree that has multiple inheritance.

Class::BlackHole just traps everything with an AUTOLOAD sub that is a no-operation.

HOWEVER, what makes Class::Blackhole different than merely:

  @Class::BlackHole::ISA = ();
  sub Class::BlackHole::AUTOLOAD { }

is that this would (unhappily) trap calls to the helpful methods in UNIVERSAL, like "can", "VERSION", and "isa". Class::BlackHole aliases those methods (or better said, all subs in package UNIVERSAL) into its own package, so that they'll be accessible instead of being caught by the AUTOLOAD.

This module provides no functions or methods.

It exports no symbols into the calling package or anywhere else.

This program is distributed in the hope that it will be useful, but without any warranty; without even the implied warranty of merchantability or fitness for a particular purpose.

But let me know if it gives you any problems, OK?

Copyright 1999, 2000, Sean M. Burke "", all rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

Sean M. Burke ""
2004-12-30 perl v5.32.1

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