Class::Trigger man page on Fedora

Man page or keyword search:  
man Server   31170 pages
apropos Keyword Search (all sections)
Output format
Fedora logo
[printable version]

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

NAME
       Class::Trigger - Mixin to add / call inheritable triggers

SYNOPSIS
	 package Foo;
	 use Class::Trigger;

	 sub foo {
	     my $self = shift;
	     $self->call_trigger('before_foo');
	     # some code ...
	     $self->call_trigger('middle_of_foo');
	     # some code ...
	     $self->call_trigger('after_foo');
	 }

	 package main;
	 Foo->add_trigger(before_foo => \&sub1);
	 Foo->add_trigger(after_foo => \&sub2);

	 my $foo = Foo->new;
	 $foo->foo;	       # then sub1, sub2 called

	 # triggers are inheritable
	 package Bar;
	 use base qw(Foo);

	 Bar->add_trigger(before_foo => \&sub);

	 # triggers can be object based
	 $foo->add_trigger(after_foo => \&sub3);
	 $foo->foo;	       # sub3 would appply only to this object

DESCRIPTION
       Class::Trigger is a mixin class to add / call triggers (or hooks) that
       get called at some points you specify.

METHODS
       By using this module, your class is capable of following methods.

       add_trigger
	     Foo->add_trigger($triggerpoint => $sub);
	     $foo->add_trigger($triggerpoint => $sub);

	     Foo->add_trigger( name => $triggerpoint,
			       callback => sub {return undef},
			       abortable => 1);

	     # no further triggers will be called. Undef will be returned.

	   Adds triggers for trigger point. You can have any number of
	   triggers for each point. Each coderef will be passed a reference to
	   the calling object, as well as arguments passed in via
	   call_trigger. Return values will be captured in list context.

	   If add_trigger is called with named parameters and the "abortable"
	   parameter is passed a true value, a false return value from trigger
	   code will stop processing of this trigger point and return a
	   "false" value to the calling code.

	   If "add_trigger" is called without the "abortable" flag, return
	   values will be captured by call_trigger, but failures will be
	   ignored.

	   If "add_trigger" is called as object method, whole current trigger
	   table will be copied onto the object and the new trigger added to
	   that. (The object must be implemented as hash.)

	     my $foo = Foo->new;

	     # this trigger ($sub_foo) would apply only to $foo object
	     $foo->add_trigger($triggerpoint => $sub_foo);
	     $foo->foo;

	     # And not to another $bar object
	     my $bar = Foo->new;
	     $bar->foo;

       call_trigger
	     $foo->call_trigger($triggerpoint, @args);

	   Calls triggers for trigger point, which were added via
	   "add_trigger" method. Each triggers will be passed a copy of the
	   object as the first argument.  Remaining arguments passed to
	   "call_trigger" will be passed on to each trigger.  Triggers are
	   invoked in the same order they were defined.

	   If there are no "abortable" triggers or no "abortable" trigger
	   point returns a false value, "call_trigger" will return the number
	   of triggers processed.

	   If an "abortable" trigger returns a false value, call trigger will
	   stop execution of the trigger point and return undef.

       last_trigger_results
	       my @results = @{ $foo->last_trigger_results };

	   Returns a reference to an array of the return values of all
	   triggers called for the last trigger point. Results are ordered in
	   the same order the triggers were run.

TRIGGER POINTS
       By default you can make any number of trigger points, but if you want
       to declare names of trigger points explicitly, you can do it via
       "import".

	 package Foo;
	 use Class::Trigger qw(foo bar baz);

	 package main;
	 Foo->add_trigger(foo  => \&sub1); # okay
	 Foo->add_trigger(hoge => \&sub2); # exception

FAQ
       Acknowledgement: Thanks to everyone at POOP mailing-list
       (http://poop.sourceforge.net/).

       Q.  This module lets me add subs to be run before/after a specific
	   subroutine is run.  Yes?

       A.  You put various call_trigger() method in your class.	 Then your
	   class users can call add_trigger() method to add subs to be run in
	   points just you specify (exactly where you put call_trigger()).

       Q.  Are you aware of the perl-aspects project and the Aspect module?
	   Very similar to Class::Trigger by the look of it, but its not
	   nearly as explicit.	Its not necessary for foo() to actually say
	   "triggers go *here*", you just add them.

       A.  Yep ;)

	   But the difference with Aspect would be that Class::Trigger is so
	   simple that it's easy to learn, and doesn't require 5.6 or over.

       Q.  How does this compare to Sub::Versive, or Hook::LexWrap?

       A.  Very similar. But the difference with Class::Trigger would be the
	   explicitness of trigger points.

	   In addition, you can put hooks in any point, rather than pre or
	   post of a method.

       Q.  It looks interesting, but I just can't think of a practical example
	   of its use...

       A.  (by Tony Bowden)

	   I originally added code like this to Class::DBI to cope with one
	   particular case: auto-upkeep of full-text search indices.

	   So I added functionality in Class::DBI to be able to trigger an
	   arbitary subroutine every time something happened - then it was a
	   simple matter of setting up triggers on INSERT and UPDATE to
	   reindex that row, and on DELETE to remove that index row.

	   See Class::DBI::mysql::FullTextSearch and its source code to see it
	   in action.

AUTHORS
       Original idea by Tony Bowden <tony@kasei.com> in Class::DBI.

       Code by Tatsuhiko Miyagawa <miyagawa@bulknews.net>.

       Jesse Vincent added a code to get return values from triggers and
       abortable flag.

LICENSE
       This library is free software; you can redistribute it and/or modify it
       under the same terms as Perl itself.

SEE ALSO
       Class::DBI

perl v5.14.0			  2009-10-11		     Class::Trigger(3)
[top]

List of man pages available for Fedora

Copyright (c) for man pages and the logo by the respective OS vendor.

For those who want to learn more, the polarhome community provides shell access and support.

[legal] [privacy] [GNU] [policy] [cookies] [netiquette] [sponsors] [FAQ]
Tweet
Polarhome, production since 1999.
Member of Polarhome portal.
Based on Fawad Halim's script.
....................................................................
Vote for polarhome
Free Shell Accounts :: the biggest list on the net