Get every folder in a given folder

[druido]

Hi,
I don’t really grasp the semantics of some operations targeted at the Finder. I hope someone would be so kind to enlighten me In particular, the following script results in a list of all the folders contained in the Downloads folder if there are any, but it produces an error if the the Downloads folder is empty:

tell application "Finder"
	every folder of (entire contents of folder (path to downloads folder))
end tell

Can someone tell me why in the latter case the result is not the empty list but the error “Can’t get every folder of folder “Downloads” of [.]”? Also, is this the fastest way (do shell script aside) to get a list of folders within a given folder?

[StefanK]

Hi,

entire contents throws an error if its container is empty.
You can catch the error this way

set downloadsFolder to (path to downloads folder)
tell application "Finder"
	try
		set folderList to every folder of (entire contents of downloadsFolder)
	on error
		set folderList to {}
	end try
end tell

Note: as path to downloads folder represents an alias, remove the keyword folder.
I also recommend to avoid any Scripting Addition command within an application tell block (if possible)

[druido]

Thanks for your reply!

entire contents throws an error if its container is empty.

Ok, so this is expected behaviour. Just I cannot find where it is documented.

I also recommend to avoid any Scripting Addition command within an application tell block (if possible)

Do you refer to path to in the above example? Could you elaborate on why this is advisable?

[StefanK]

@druido

Thanks for your reply!

entire contents throws an error if its container is empty.

Ok, so this is expected behaviour. Just I cannot find where it is documented.

I don’t know, whether this is the expected behaviour, indeed this is the behaviour

@druido

I also recommend to avoid any Scripting Addition command within an application tell block (if possible)

Do you refer to path to in the above example? Could you elaborate on why this is advisable?

It could cause terminology clahes, for example Mail.app “translates” path to into for rule or something similar. Even Apple recommends to avoid Scripting Additions commands within application tell blocks

[Marc_Anthony]

Entire contents actually does produce an empty list, but there are three operations in that line, the third of which is a get folders. The empty list was already realized prior to that, and there are no folders in an empty list.

[Nigel_Garvey]

@StefanK

entire contents throws an error if its container is empty.

To be exact, it’s the extended reference every of (entire contents .) which errors if that particular kind of element doesn’t exist in the folder.

Perversely, a filter does work both in either case:

tell application "Finder"
	every item of (entire contents of folder (path to downloads folder)) whose class is folder
end tell

If you’re looking for files by this method, though, you have to be specific about the class(es) of file (ie. document file, application file, etc.)

[druido]

I also recommend to avoid any Scripting Addition command within an application tell block (if possible) [.] It could cause terminology clahes [.]

Interesting, I’ve never thought about it. I’ll keep it in mind.

Entire contents actually does produce an empty list, but there are three operations in that line, the third of which is a get folders. The empty list was already realized prior to that, and there are no folders in an empty list.

I see. That starts to make sense to me.

Indeed. entire contents alone does return an empty list.

Perversely, a filter does work both in either case

Is AppleScript surprising, or what? In my tests, though, using a filter is about 10 times slower than using every folder of (entire contents of.)