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#!/usr/bin/env ruby
# XMMS2 - X Music Multiplexer System
# Copyright (C) 2003-2007 XMMS2 Team
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# Lesser General Public License for more details.
# This file is a part of the XMMS2 client tutorial #3.
# For the purposes of this tutorial, the client will fetch the mediainfo on the
# currently playing song. If you're favorite song is still playing, you're in
# luck. If not, start it up again; show your favorite artist you're the #1 fan!
require 'xmmsclient'
# Ruby is a beautiful and elegant language, and I would be remiss if I didn't
# use it as such. So I'm taking advantage of Ruby's object-orientation here and
# chaining some methods together to produce shorter code. You already had
# plenty of exposure to these methods anyway, so you won't need them typed out
# explicitly.
begin
# The connect method returns itself, so 'xmms' still holds an Xmms::Client
# object.
xmms = Xmms::Client.new('tutorial3').connect(ENV['XMMS_PATH'])
rescue Xmms::Client::ClientError
puts 'Failed to connect to XMMS2 daemon.'
puts 'Please make sure xmms2d is running and using the correct IPC path.'
exit
end
# Taking the last tutorial one step further, the value from the
# playback_current_id call will be used in another clientlib call. To make a
# a practical client, you'll often have to chain calls like this. We get the ID
# of the current song via the 'value' method, then use it as an argument to
# the medialib_get_info call, which takes an ID as its only argument.
begin
# Just like above with the 'connect' method, the 'wait' method returns
# itself, too. So the 'value' method is still called on an Xmms::Result
# object, and we eliminate the variable 'res,' which might be nicer on our
# computer's memory, and Ruby's garbage collector.
id = xmms.playback_current_id.wait.value
if(id == 0)
puts 'There is no current ID. XMMS2 is probably not playing anything.'
else
begin
# You've been using IDs for a while now and maybe you don't yet
# understand their exact importance in the XMMS2 world. The
# medialib stores a huge table of songs and associated information.
# Each song is identifiable by a unique ID that can be used to look
# up all other associated information. Here, the medialib_get_info
# call is given an ID and should return all the mediainfo
# associated with that ID.
# Just like before, I've used Ruby's beautiful syntactic sugar to
# condense this code down to one line and eliminate another
# variable. Just like you can say, "Get the mediainfo for ID, wait
# on it, and return a value," in one sentence, you can say it in
# one, beautifully simple line of Ruby. Doesn't Ruby just feel so
# right?
info = xmms.medialib_get_info(id).wait.value
# We'll print a pretty table of mediainfo for this ID, and so we'll
# make a nice header for it, too.
puts "Server mediainfo for ID: #{id}"
# The value we just retrieved and stored in 'info' is a so-called
# propdict (property dictionary). It's a clever way of storing and
# accessing mediainfo in a way that also includes the source of the
# mediainfo. Why, you ask? Let me explain by example. You're
# listening to your favorite icecast broadcast with XMMS2. You
# notice that both icecast and the vorbiscomments in the streaming
# vorbis contain some tags that describe the stream. But the stream
# source has improperly-tagged vorbis files that it sources and all
# the Russian songs you love have mangled titles. You want to look
# at the stream metadata that icecast provides to see your
# that glorious Cyrillic as the authors intended.
# This is where propdicts are handy. In XMMS2, your icecast stream
# is going through several transform plugins (xforms) before you
# it gets to your speakers. One of those plugins is the
# 'icymetaint' xform, which grabs tags from the icecast stream
# itself and stores them in the medialib. Another xform that your
# stream passes through is the vorbis decoder, which reads the
# vorbiscomment block into the medialib.
# If you used a regular dict (or Hash, in Ruby terminology) the
# tags from the vorbis decoder would always wind up overwriting the
# tags from the icymetaint xform. With a propdict, you can look at
# the tags from a certain source. You can write a little program to
# display the Russian tags as you wanted.
# Now for the nitty-gritty. Ruby's propdict implementation is in
# the Xmms::PropDict class. PropDict uses Symbols as keys because
# they are light and fast. Sources are Strings, however, since they
# they are not (directly) used to access values. And sources have
# naming conventions like 'server' for the server, 'plugin/foo' for
# plugin 'foo,' and 'client/bar' for a client 'bar.' PropDicts can
# masquerade as regular Hashes, which means info[:artist] will
# return the artist from only one source. (There are some
# precedence rules, which I won't go into here.) But we want to
# print out all the mediainfo in a big table, so we won't use
# info[], we'll use an 'each' method instead. The 'each' method is
# similar to Hash#each, except that there's an additional source
# argument passed to the block.
info.each_pair { |key, data|
data.each_pair { |src, val|
puts "[#{src}] #{key} = #{val}"
}
}
# Wow, that whole table was printed out with one line of code!
# And, of course we check for errors since we want a bulletproof
# client. No disgruntled users can moan about crashes.
rescue Xmms::Result::ValueError
puts 'There was an error retrieving mediainfo for the current ID.'
end
end
# If the begin..rescue..end block within this one was not used, the exception
# would fall through to this block and print out this error message. You can
# write shorter code this way at the expense of less accurate error messages. I
# certainly don't advocate this, and you should always be careful to catch
# errors as it helps greatly with debugging.
rescue Xmms::Result::ValueError
puts 'There was an error retrieving the current ID.'
end
# There's still bigger and better to move on to. Proceed to the next tutorial
# and learn how to work with playlists and handle PropDicts in new ways.
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