On Apache
Under GNU General Public License
2024-12-13 00:35 @18.222.112.142 CrawledBy Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko; compatible; ClaudeBot/1.0; +claudebot@anthropic.com)
Class::Trigger(3pm) User Contributed Perl Documentation Class::Trigger(3pm)
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 arbitrary 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 AT kasei.com> in Class::DBI.
Code by Tatsuhiko Miyagawa <miyagawa AT 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 v5.30.0 2020-04-08 Class::Trigger(3pm)
Generated by $Id: phpMan.php,v 4.55 2007/09/05 04:42:51 chedong Exp $ Author: Che Dong
On Apache
Under GNU General Public License
2024-12-13 00:35 @18.222.112.142 CrawledBy Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko; compatible; ClaudeBot/1.0; +claudebot@anthropic.com)