/ 
Map-Metro-0.2405
River stage two • 19 direct dependents • 19 total dependents
/ Map::Metro::Hook

NAME

Map::Metro::Hook - Hook into Map::Metro

VERSION

Version 0.2405, released 2016-07-23.

SYNOPSIS

use Map::Metro;

my $graph = Map::Metro->new('Helsinki', hooks => ['Helsinki::Swedish'])->parse;

# Now all station names are in Swedish

my $graph2 = Map::Metro->new('Helsinki', hooks => ['Helsinki::Swedish', 'StreamStations'])->parse;

# Station names are in Swedish, as before, but they are also printed as they are
# added from the map file. See more on StreamStations below.

DESCRIPTION

Hooks are a powerful way to interact (and change) Map::Metro while it is building the network or finding routes.

Hooks are implemented as classes in the Map::Metro::Plugin::Hook namespace.

Hooks

All hooks get the hook class instance as its first parameter, and can beyond that receive further parameters depending on where they hook into Map::Metro.

There are currently two hooks (events) available:

before_add_station($plugin, $station)

$station

The Map::Metro::Graph::Station object that is about to be added.

This event fires right before the station is added to the Map::Metro::Graph object. Especially useful for enabling translations of station names.

before_add_routing($plugin, $routing)

$routing

The Map::Metro::Graph::Routing object that is about to be added.

This event fires after a routing has been completed (all routes between two Stations has been found).

This is useful for printing routings as they are found rather than waiting until all routings are found.

Used by the bundled PrettyPrinter hook. That also serves as a good template for customized hooks.

Custom hooks

Two things are necessary for a hook class. It must...

...live in the Map::Metro::Plugin::Hook namespace.

...have a register method, that returns a hash where the key is the hook type and the value the sub routine that should be executed when the event is fired. Since register returns a hash, one Plugin::Hook class can hook into more than one event.

Example

Take a look at Map::Metro::Plugin::Hook::StreamStations.

The StreamStations hook mentioned in the synopsis, and included in this distribution, looks like this:

package Map::Metro::Plugin::Hook::StreamStations;

use Moose;
use Types::Standard -types;

has station_names => (
    is => 'rw',
    isa => ArrayRef,
    traits => ['Array'],
    handles => {
        add_station_name => 'push',
        all_station_names => 'elements',
        get_station_name => 'get',
    },
);

sub register {
    before_add_station => sub {
        my $self = shift;
        my $station = shift;

        say $station->name;
        $self->add_station_name($station->name);
    };
}
}

1;

It does two things, as stations are parsed from the map file and the before_add_station method is executed for every station:

* It prints all station names.

* It adds all station names to the station_names attribute.

So if you instantiate your graph like this:

my $graph = Map::Metro->new('Helsinki', hooks => ['Helsinki::Swedish', 'StreamStations'])->parse;

You can then access this station_names attribute like this:

my $station_streamer = $graph->get_plugin('StreamStations');

my @station_names = $station_streamer->all_station_names;
my $special_station = $station_streamer->get_station_name(7);

SOURCE

https://github.com/Csson/p5-Map-Metro

HOMEPAGE

https://metacpan.org/release/Map-Metro

AUTHOR

Erik Carlsson <info@code301.com>

COPYRIGHT AND LICENSE

This software is copyright (c) 2016 by Erik Carlsson.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.