Jan 2011

Opening a Finder's window from Impromptu (alas how to use the applescript bridge..)


Imagine you've got a bunch of audio samples you want to load up while livecoding with Impromptu but you can't remember exactly their names - it'd be handy to be able to open up the corresponding Finder window directly from scheme, without too much clicking around. Do-able or not?

I spent some time trying to figure this out, and the answer is yes! Quite a nice learning experience... although it came with a surprise at the end.

Originally I thought, let's do it via impromptu's ObjC bridge. I don't know much about ObjC but after a bit of googling it seemed evident that the quickest way to accomplish this is by writing ObjC code that, in turns, runs a simple applescript command that opens a window:

[NSString](http://developer.apple.com/documentation/Cocoa/Reference/Foundation/Classes/NSString_Class/) \*s \= \[[NSString](http://developer.apple.com/documentation/Cocoa/Reference/Foundation/Classes/NSString_Class/) stringWithFormat:  
     @"tell application "Terminal" to do script "cd %@"", folderPath];  

[NSAppleScript](http://developer.apple.com/documentation/Cocoa/Reference/Foundation/Classes/NSAppleScript_Class/) \*as \= \[\[[NSAppleScript](http://developer.apple.com/documentation/Cocoa/Reference/Foundation/Classes/NSAppleScript_Class/) alloc\] initWithSource: s\];  
[as executeAndReturnError:nil];

So I translated the bottom part of the code above into impromptu/scheme:

(define run_applescript  
   (lambda (script)  
      (objc:call (objc:call (objc:call "NSAppleScript" "alloc")  
                            "initWithSource:"  
                            script)  
                 "executeAndReturnError:" )))

That is a generic script-running function, that is, you can pass any script and it'll run it, eg:

(define script0 "  
   tell application "Finder" to open folder "Macintosh HD:Users"  
   tell application "Finder" to activate")  


(define script1 "  
   tell application "Terminal" to do script "cd ~; open ."")  


(define script2 "  
                tell application "System Events"n  
                tell dock preferencesn  
                set properties to {autohide:false}n  
                end telln  
                end tell")  

;; finally, let's choose randomly one of the scripts above and run it  
(run_applescript (random '(script0 script1 script2)))

Now, back to the original problem: in order to open a Finder's window at a specified location we need to pass the location variable to our function run_applescript; also, we want to be able to pass unix path expressions (eg '/Users/mike/music/'), so we've got to transform that path syntax into the semicolon-delimited macintosh syntax ("Macintosh HD:Users:mike:music") needed by the applescript function we're using. That's easily done with string-replace, so here we go:

(define open_finder_at  
   (lambda (location)  
      (let* ((llocation (string-replace location "/" ":"))  
              (script (string-append "tell application "Finder" to activate open folder "Macintosh HD" llocation """)))  
         (objc:call (objc:call (objc:call "NSAppleScript" "alloc")  
                               "initWithSource:"  
                               script)  
                    "executeAndReturnError:" ))))  


(open_finder_at "/Users/me/")

That's pretty much it really... now we can easily open OsX Finder's windows from within Impromptu.

But as I said above, there's a surprise: after getting this far I thought I'd search impromptu's mailing list for more examples of obj:call .... and guess what, there's already a system function that runs applescripts, it's called sys:run-applescript !

Too bad, it's been a rewarding learning experience anyways...

Cite this blog post:


Michele Pasin. Opening a Finder's window from Impromptu (alas how to use the applescript bridge..). Blog post on www.michelepasin.org. Published on Jan. 29, 2011.

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