On 3 Oct 2008, at 17:09, Mr. Gecko wrote:
On Thu, Oct 2, 2008 at 9:52 PM, Mr. Gecko wrote:
I know but I can't find out the AppleEvent for Play Playlist.
Is there some sort of a program that will parse the AppleScript
and make an
cocoa AppleEvent code.
If you just want the raw four-char-codes from an application's
dictionary so you can construct NSAppleEventDescriptors yourself,
you can obtain them in various ways: [...]
I already looked at that but it doesn't have an actual code for Play
Playlist
I found this though <class name="playlist" code="cPly"
description="a list of songs/streams" inherits="item"
plural="playlists"> which if you look at the output of AEDebugSends
than you can see that that is called when running the play playlist
command.
I think you're a bit confused about how iTunes' Apple event API works.
This is understandable, given how hopelessly inadequate 99% of
scriptable applications' documentation is, along with the rather
unusual, counter-intuitive way that Apple event IPC works in the first
place.
Suffice it to say: nothing in AppleScript makes sense except in the
light of RPC plus queries[1][2].
IOW, you can either approach it on its own terms and accept it for
what it is, which will weird you out till you get your head around it;
or else you can try to approach it in conventional OO terms, in which
case it will frequently confuse and frustrate you whenever it behaves
in a non-OO fashion (which is quite often).
Regarding the playing of iTunes playlists, here's a quick attempt to
clarify:
iTunes has no 'play playlist' command as you suggest. There is,
however, a 'play' command (Apple event), and various kinds of playable
objects: sources, several kinds of playlists (audio CD playlists,
library playlists, user playlists, etc), and several kinds of tracks
(file tracks, URL tracks, etc).
To use the 'play' command, you construct a query ("reference" in
AppleScript jargon) identifying the object you want played, then pass
that query as the 'play' command's direct parameter. e.g.:
play (source 1)
play (source "Library")
play (playlist "My Top Rated")
play (first playlist whose name is "My Top Rated")
play (user playlist "My Top Rated")
play (user playlist "My Top Rated" of source 1)
play (track 1 of user playlist "My Top Rated")
play (file track id 56315 of user playlist id 520 of source id 41)
etc.
As you can see, queries can be pretty flexible in how they identify
objects. But whatever query you use, it's up to iTunes' 'play' event
handler to evaluate that query in order to locate the object or
objects to act upon, and do its funky thing.
Oh, and BTW: one thing you will almost never find provided by
applications' scripting documentation (be it built-in dictionaries and/
or supplementary files) is any formal indication of which commands can
operate on which objects, so expect to use some intelligent guesswork
and trial-and-error testing to figure this out for yourself. (Yes,
this sucks; AppleScripters have been kvetching about it for the last
decade, without notable effect. It's just something you'll have to
deal with; the AppleScript-users list is good for advice, and there's
a whole stack of existing iTunes scripts at <http://dougscripts.com>
to learn from.)
...
If you want to try to wrap your head around the "AppleScript way",
chapter 2 in the appscript manual tries to provide a quick summary of
the concepts involved. There's also an excellent paper by William Cook
(one of the original AppleScript designers), which describes both the
language and the Apple event-based IPC system created around it, and
provides significant insights into the original motives and decisions
behind its design. It dates back to the early days of AppleScript so
doesn't discuss the more recent related Cocoa-based APIs, but the
underlying principles are unchanged:
http://www.cs.utexas.edu/users/wcook/Drafts/2006/ashopl.pdf
Matt Neuburg's "AppleScript: The Definitive Guide" also provides a
good, critical, programmer-friendly guide to AppleScript and
application scripting principles; obviously a big chunk of the book is
about AppleScript itself which might not be of so much interest to
you, but I've heard at least one other non-AppleScript user say that
they've found it helpful, albeit after a slow start (presumably the
basic AppleScript language chapters).
HTH
has
[1] (With apologies to Theodosius Dobzhansky.)
[2] FWIW, it is an odd and unfamiliar way to do IPC, and there are a
lot of real-life design and implementation shortcomings that make it
much more difficult than it ought to be, but at a basic level it is a
logical and self-consistent - and even somewhat elegant (if unusual) -
system. The nearest analogy I can think of is using XPath queries over
XML-RPC, if that helps.
--
Control AppleScriptable applications from Python, Ruby and ObjC:
http://appscript.sourceforge.net
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