| Net::Async::MPD(3pm) | User Contributed Perl Documentation | Net::Async::MPD(3pm) |
Net::Async::MPD - A non-blocking interface to MPD
use Net::Async::MPD;
my $mpd = Net::Async::MPD->new(
host => 'localhost',
auto_connect => 1,
);
my @subsystems = qw( player mixer database );
# Register a listener
foreach my $subsystem (@subsystems) {
$mpd->on( $subsystem => sub {
my ($self) = @_;
print "$subsystem has changed\n";
# Stop listening if mixer changes
$mpd->noidle if $subsystem eq 'mixer';
});
}
# Send a command
my $stats = $mpd->send( 'stats' );
# Or in blocking mode
my $status = $mpd->send( 'status' )->get;
# Which is the same as
$status = $mpd->get( 'status' );
print 'Server is in ', $status->{state}, " state\n";
print 'Server has ', $stats->get->{albums}, " albums in the database\n";
# Put the client in looping idle mode
my $idle = $mpd->idle( @subsystems );
# Set the emitter in motion, until the next call to noidle
$idle->get;
Net::Async::MPD provides a non-blocking interface to an MPD server.
MPD supports sending command lists to make it easier to perform a series of steps as a single one. No command is executed until all commands in the list have been sent, and then the server returns the result for all of them together. See the MPD documentation <https://musicpd.org/doc/protocol/command_lists.html> for more information.
Net::Async::MPD fully supports sending command lists, and makes it easy to structure the results received from MPD, or not to if the user so desires. See the "send" method for more information.
Most operations in this module return Future objects, and to keep things consistent, any errors that are encountered during processing will result in those futures being failed or canceled as appropriate.
This module also makes use of the events in Role::EventEmitter, which provides it's own method for error handling: the "error" event. Normally, if a class "does" that role, it is expected that users will register some listener to the "error" event to handle failures. However, since errors are alredy being handled by the Futures (one woudl hope), this distribution registers a dummy listener to the "error" event, and turns into one that is mostly useful for debugging and monitoring.
Of course, the author cannot really stop overly zealous users from unsubscribing the error dummy listener, but they do so at their own risk.
MPD normally returns results as a flat list of response lines. Net::Async::MPD tries to make it easier to provide some structure to these responses by providing pre-set parser subroutines for each command. Although the default parser will be fine in most cases, it is possible to override this with a custom parser, or to disable the parsing entirely to get the raw lines from the server. For information on how to override the parser, see the documentation for the "send" method.
By default, the results of each command are parsed independently, and passed to the Future returned by the corresponding call to "send". This is true regardless of whether those commands were sent as part of a list or not.
This means that, by default, the Future that represents a given call to "send" will receive the results of as many commands as were originall sent.
This might not be desirable when eg. sending multiple commands whose results should be aggregated. In those cases, it is possible to flatten the list by passing a false value to the "list" option to "send" or "get".
This means that when calling
($stats, $status) = $mpd->get(
{ list => 1 }, # This is the default
[ 'stats', 'status' ]
);
$stats and $status will each have a hash reference with the results of their respective commands; while when calling
$combined_list = $mpd->get( { list => 0 }, [
[ search => artist => '"Tom Waits"' ],
[ search => artist => '"David Bowie"' ],
]);
$combined_list will hold an array reference with the combined results of both "search" commands.
$future = $mpd->send( 'status' );
$future = $mpd->send( { parser => 'none' }, 'stats' );
$future = $mpd->send( search => artist => '"Tom Waits"' );
# Note the dumb string quoting
$future = $mpd->send( { list => 0 }, [
[ search => artist => '"Tom Waits"' ],
[ search => artist => '"David Bowie"' ],
]);
$future = $mpd->send( \%options, 'stats', sub { ... } );
Asynchronously sends a command to an MPD server, and returns a Future. For information on what the value of this Future will be, please see the "Server Responses" section.
This method can be called in a number of different ways:
If sending multiple commands in one request, the "command_list..." commands can be left out and they will be automatically provided for you.
An optional subroutine reference passed as the last argument will be set as the the "on_ready" of the Future, which will fire when there is a response from the server.
A hash reference with additional options can be passed as the first argument. Valid keys to use are:
Defaults to true. This value is ignored when not sending a command list.
Alternatively, if the value itself is a code reference, then that will be called as
$parser->( \@response_lines, \@command_names );
Where each element in @response_lines is a reference to the list of lines received after completing the corresponding element in @command_names.
When setting "list" to false, @response_lines will have a single value, regardless of how many commands were sent.
For ease of use, underscores in the final command name will be removed before sending to the server (unless the command name requires them). So
$client->send( 'current_song' );
is entirely equivalent to
$client->send( 'currentsong' );
If called with a list of subsystem names, then the client will only listen to those subsystems. Otherwise, it will listen to all of them.
If you are using this module for an event-based application (see below), this will configure the client to fire the events at the appropriate times.
Returns a Future. Waiting on this future will block until the next call to noidle (see below).
As this is provided by the server, this is "undef" until after a connection has been established with the "connect" method, or by setting "auto_connect" to true in the constructor.
Net::Async::MPD does the Role::EventEmitter role, and inherits all the methods defined therein. Please refer to that module's documentation for information on how to register subscribers to the different events.
The method is called with two subroutine references. The first is subscribed as a regular listener, and the second is called only when the first one returns a true value. At that point, the entire set is unsubscribed.
After calling idle, the client will be in idle mode, which means that any changes to the specified subsystems will trigger a signal. When the client receives this signal, it will fire an event named like the subsystem that fired it.
The event will be fired with the client as the first argument, and the response from the server as the second argument. This can safely be ignored, since the server response will normally just hold the name of the subsystem that changed, which you already know.
The existing events are the following, as defined by the MPD documentation.
A previous attempt at writing this distribution, based on AnyEvent. Although the design is largely the same, it is not as fully featured or as well tested as this one.
A lightweight blocking MPD library. Has fewer dependencies than this one, but it does not currently support command lists. I took the idea of allowing for underscores in command names from this module.
The original version of this module, which used AnyEvent. The interface on both of these modules is virtually identical.
The first MPD library on CPAN. This one also blocks and is based on Moose. However, it seems to be unmaintained at the moment.
A Dancer plugin to connect to MPD. Haven't really tried it, since I haven't used Dancer...
A POE component to connect to MPD. This uses Audio::MPD in the background.
This software is copyright (c) 2017-2018 by José Joaquín Atria.
This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.
| 2022-11-20 | perl v5.36.0 |