Configuration Files As Extensions
A ConfigFile may be enough to customize the module for reasonable needs. It may also specify modules by name to be created and employed in a framework.
# the config.pl file defines @listeners to contain a list of class names # that should receive notices from an EventListener broadcaster, # referenced by $broadcaster. require 'config.pl'; foreach my $listener (@listeners) { require $listener; my $list_inst = $listener->new; $broadcaster->add_listener($list_inst); }See Event listener for the broadcaster/listener idiom. This avoids building the names of listener modules into the application. An independent author could write a plugin to this application: she would need only have the user modify //config.pl// to include mention of the plugin. Of course, modification of //config.pl// could be automated. The install program for the plugin would need to ask the user where the //config.pl// is, and use the ConfigFile idiom to update it.
Read more about this topic: Extensibility Pattern
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