POSIX file Returning scpt Object

Scripting Forums AppleScriptObjC and Xcode
#1

I’m baffled about some code that works fine in Script Debugger but fails when run within an ASOC app.

When the following is run in Xcode, the “POSIX file” assignment returns a ‘scpt’ object instead of ‘furl’.


set x to POSIX file "/"
log class of x
-- <NSAppleEventDescriptor: 'scpt'>
log x
-- <AppDelegate @0x608000225f20: OSAID(4) ComponentInstance(0x810000)>

log class of (POSIX file "/")
-- <NSAppleEventDescriptor: 'furl'>
log (POSIX file "/") as string
-- Can't make «script» into type string. (error -1700)

In Script Debugger I get what I would expect:


set x to POSIX file "/"
log class of x
-- <<class furl>>
log x
-- "Macintosh:HD"

log class of (POSIX file "/")
-- <<class furl>>
log (POSIX file "/") as string
-- "Macintosh:HD"

What’s going on here?

Thanks,
Lance

#2

In AppleScriptObjC you have to write

 set x to  "/" as POSIX file

POSIX file x does not work

#3

Ah, researching that further, it’s the difference between “coercion” versus an “object specifier”. A subtle but important concept I have yet to learn!

Frustrating the developer docs don’t mention the “as POSIX file” notation.

https://developer.apple.com/library/content/documentation/LanguagesUtilities/Conceptual/MacAutomationScriptingGuide/ReferenceFilesandFolders.html

Thanks!

#4

PS. Any insight as to why the execution environment of Xcode behaves so different from Script Debugger in this case?

#5

Simply spoken

“ The ScriptDebugger environment is AppleScript.
“ The Xcode environment is Objective-C bridged to AppleScript.

#6

Further to Stefan’s answer:

AppleScript’s log command does nothing itself. What you see logged in Script Debugger or Script Editor is produced by the editor itself, which retrieves a “human readable” form of the AppleScript object in question.

In Xcode, log takes advantage of the normal NSLog-style logging system, which requires Cocoa objects, so AppleScript objects first have to be converted to Cocoa equivalents.

#7

Thanks for the clarification. I just equated ‘log’ to doing a ‘printf’ but was always curious why Script Debugger output is not formatted as just a series of log lines. Now I know it’s because SD is free to do it’s own thing with log statements!

#8

The Xcode environment is running your newly build application against Xcode’s debugger. A debugger like in SD is not debugging a process but debugging AppleScript’s own VM. This is the big difference between these two.

SD is like debugging JavaScript code using Chrome’s built-in development tools.
Xcode is like running Chrome in GDB trying to debug JavaScript code using GDB.