Getting directory of input file (Applescript) - applescript

Question

I'm confused - I've been googling for an hour and have tried probably ten different forms of set posixDirectory to POSIX path of (parent of (path to aFile) as string) but I can't seem to get it right.
I'm getting the full POSIX path (including the filename) by doing
set posixFilePath to POSIX path of aFile
Now, how do I get the POSIX path of just the directory?? I'm getting various errors depending on what I do... can't make alias.. can't get parent of alias...
I would think this should work but it's not...
set posixDirectory to POSIX path of ((parent of aFile))

Answer 1

There are couple of ways to do this if you already have the initial path.
From Posix path format
set thePath to "/Users/USERNAME/Documents/Test/selectedTextColour.css"
set textNumber1 to characters 1 thru -((offset of "/" in (reverse of items of thePath as string)) + 1) of thePath as string
or using shell
set thePath to "/Users/USERNAME/Documents/Test/selectedTextColour.css"
set parentPath to do shell script "dirname " & quoted form of thePath
Result: "/Users/USERNAME/Documents/Test"
From Posix file format
set thePath to "Macintosh HD:Users:USERNAME:Documents:Test:selectedTextColour.css"
set textNumber1 to characters 1 thru -((offset of ":" in (reverse of items of thePath as string)) + 1) of thePath as string
Result: "Macintosh HD:Users:USERNAME:Documents:Test"

Answer 2

Use the container command of Finder:
set aFile to choose file
tell application "Finder" to set posixDirectory to POSIX path of ((container of aFile) as text)

Answer 3

This should be sufficient really, when you already have the posix path of a file.
to parentFolOfPxPath for pxPath
-- Assumes no superfluous slashes
set {tids, text item delimiters, i} to {text item delimiters, "/", ((pxPath ends with "/") as integer) + 1}
set {parFol, text item delimiters} to {text 1 thru text item -(i + 1) of pxPath, tids}
return parFol
end parentFolOfPxPath

Answer 4

Try the subroutine parentFolderOf(localPath). localPath can be an alias, alias as text or a posix path. It returns a reference that you can use with Finder, like this:
set thisItem to parentFolderOf(path to fonts folder)
tell application "Finder" to reveal thisItem
Here the script:
log (path to fonts folder)
log parentFolderOf(path to fonts folder)
log parentFolderOf(POSIX path of (path to fonts folder as text)) as text
log parentFolderOf("/System")
log parentFolderOf("/System") as text
# lets generate an error:
# parentFolderOf("ThisGeneratesAnError")
on parentFolderOf(localPath)
if (class of localPath is text) and (localPath contains ":") then
try
set localPath to localPath as alias
on error
error "File missing!"
end try
end if
# if its not an alias and not text containing ":" we assume its a posix path
if not (class of localPath is alias) then
try
set localPath to (localPath as POSIX file) as alias
on error
error "File missing!"
end try
end if
-- get the container:
set localPathContainerPath to ""
tell application "Finder"
try
set localPathContainerPath to (get container of localPath)
end try
end tell
return localPathContainerPath
end parentFolderOf
Addition McUsr's approach seems to be a good strategy because there is no need to use Finder (which will throw an error if the item is missing). Here a version whose input works with alias, (alias as text) or posix path:
log (parentFolder for (path to me))
log (parentFolder for "/Root/Sub1/Sub2/Sub3/testFile.txt")
log (parentFolder for "/Root/Sub1/Sub2/Sub3////")
log (parentFolder for "///Root/Sub1/Sub2/Sub3////")
log (posixPath for (path to me))
to parentFolder for aPath
set aPath to posixPath for aPath
set {tids, text item delimiters, i} to {text item delimiters, "/", ((aPath ends with "/") as integer) + 1}
set {pF, text item delimiters} to {text 1 thru text item -(i + 1) of aPath, tids}
return pF
end parentFolder
to posixPath for aPath
if class of aPath is not text then set aPath to aPath as text
if aPath contains ":" then set aPath to POSIX path of aPath
repeat while aPath starts with "//"
set aPath to (characters 2 thru -1 of aPath) as text
end repeat
repeat while aPath ends with "//"
set aPath to (characters 1 thru -2 of aPath) as text
end repeat
return aPath
end posixPath