1Callback(3)           User Contributed Perl Documentation          Callback(3)
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NAME

6       Callback - object interface for function callbacks
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SYNOPSIS

9               use Callback;
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11               my $callback = new Callback (\&myfunc, @myargs);
12               my $callback = new Callback ($myobj, $mymethod, @myargs);
13               my $callback = new Callback ($old_callback, @myargs);
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15               $callback->call(@some_more_args);
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DESCRIPTION

18       Callback provides a standard interface to register callbacks.  Those
19       callbacks can be either purely functional (i.e. a function call with
20       arguments) or object-oriented (a method call on an object).
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22       When a callback is constructed, a base set of arguments can be
23       provided.  These function arguments will preceed any arguments added at
24       the time the call is made.
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26       There are two forms for the callback constructor, depending on whether
27       the call is a pure functional call or a method call.  The rule is that
28       if the first argument is an object, then the second argument is a
29       method name to be called on that object.  Method resolution happens at
30       the time the Callback object is built: an error will be raised if it
31       cannot be found.
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33       Callback objects built for object-oriented calls also have the property
34       of being serializable via Storable.  Purely functional callabacks
35       cannot be serialized because CODE references are not supported by
36       Storable.
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38       Callback objects can be created from existing Callback objects.  Any
39       arguments will be appended onto the original list of arguments.
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TRACING

42               use Callback qw(@callbackTrace);
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44       If you're writing a debugging routine that provides a stack-dump (for
45       example, Carp::confess) it is useful to know where a callback was
46       registered.
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48               my $ct = 0;
49               while (($package, $file, $line, $subname, $hasargs, $wantarray) = caller($i++)) {
50                   ...
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52                   if ($subname eq 'Callback::call') {
53                       print "callback registered $Callback::callbackTrace[$ct]\n";
54                       $ct++;
55                   }
56               }
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58       Without such code, it becomes very hard to know what's going on.
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61       Copyright (C) 1994, 2000, 2002 David Muir Sharnoff.   All rights
62       reserved.  This module may be licensed on the same terms as Perl
63       itself.
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AUTHORS

66       David Muir Sharnoff <muir@idiom.com> and Raphael Manfredi
67       <Raphael_Manfredi@pobox.com>
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SEE ALSO

70       Storable(3).
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74perl v5.30.0                      2019-07-26                       Callback(3)
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