[MacRuby-devel] NSNotificationCenter observers, selectors and notifications

24 Apr 2010

      Hi peoples,

I'm not sure if I'm doing something wrong here, or if it's a bug.  I'm trying to get a notification when a quicktime track finishes playing.  The documentation for NSNotificationCenter says:

notificationSelector
Selector that specifies the message the receiver sends notificationObserver to notify it of the notification posting. The method the selector specifies must have one and only one argument (an instance of NSNotification).

yet, if I use a selector that takes one argument, there is an error when the NSNotificationCenter tries to notify me:
2010-04-24 12:06:49.587 macruby[5042:903] -[Player track_finished_with_notifier]: unrecognized selector sent to instance 0x2002c3d40

On the other hand, if I give a selector that doesn't take any arguments at all, it is in fact called by the NSNotificationCenter at the right moment.

I've included a quickly hacked up script that shows the problem at the end of this message.  I'm using macruby 0.5 on Snow Leopard, so maybe the bug (if it is indeed a bug, and not an error on my part) is already fixed...  To run the script you'll have to replace Evanescence and Going Under with a group/track that you have in your iTunes library...

Alli

#!/usr/local/bin/macruby

require 'rubygems'
require 'hotcocoa'

framework 'Cocoa'
framework 'QtKit'

include HotCocoa

class Player
	def init
	  NSNotificationCenter.defaultCenter.addObserver(self, selector: :track_finished, name:QTMovieDidEndNotification, object:nil)
	  NSNotificationCenter.defaultCenter.addObserver(self, selector: :track_finished_with_notifier, name:QTMovieDidEndNotification, object:nil)
	  movie = getQtMovieFromArtist('Evanescence', track:'Going Under')
	  movie.volume = 30
	  movie.play
	  puts "playing..."
	  sleep(10)
	  self
  end

	def getQtMovieFromArtist( artist, track:track_name)
		iTunesXMLPath = "#{NSHomeDirectory()}/Music/iTunes/iTunes Music Library.xml"
    iTunesData = NSDictionary.alloc.initWithContentsOfFile(iTunesXMLPath)
    tracks = iTunesData.objectForKey('Tracks')
    artist_db = tracks.find_all { |track| track[1]['Artist'] == artist}
    track_db = artist_db.find{|track| track[1]['Name'] == track_name}
    url = NSURL.URLWithString(track_db[1]['Location'])
    errorptr = Pointer.new_with_type('@')
    movie = QTMovie.movieWithURL(url, error:errorptr)
    if (!movie)
      error = errorptr[0]
      puts "Error loading song: #{track_db[1]['Name']}  #{error.code} #{error.localizedDescription}"
    end
    movie
	end

	def track_finished
	  NSLog( "track finished!")
	end

	def track_finished_with_notifier(notifier)
	  NSLog("track finished with notifier #{notifier}")
  end

end

class Application
  def start
    application :name => "Player" do |app|
      app.delegate = self
      Player.new
    end
  end

  def on_new(sender)
    Player.new
  end

  def on_close(sender)
    w = NSApp.mainWindow
    if w
      w.performClose self
    else
      NSBeep()
    end
  end

  def on_clear(sender)
    w = NSApp.mainWindow
    if w and w.respond_to?(:terminal)
      w.terminal.clear
    else
      NSBeep()
    end
  end

end

Application.new.start

[MacRuby-devel] NSNotificationCenter observers, selectors and notifications

Allison Newman