Mail "Can't continue" for a AppleScript function - email

Question

I'm trying to write an AppleScript for use with Mail (on Snow Leopard) to save image attachments of messages to a folder. The main part of the AppleScript is:
property ImageExtensionList : {"jpg", "jpeg"}
property PicturesFolder : path to pictures folder as text
property SaveFolderName : "Fetched"
property SaveFolder : PicturesFolder & SaveFolderName
tell application "Mail"
set theMessages to the selection
repeat with theMessage in theMessages
repeat with theAttachment in every mail attachment of theMessage
set attachmentFileName to theAttachment's name
if isImageFileName(attachmentFileName) then
set attachmentPathName to SaveFolder & attachmentFileName
save theAttachment in getNonexistantFile(attachmentPathName)
end if
end repeat
end repeat
end tell
on isImageFileName(theFileName)
set dot to offset of "." in theFileName
if dot > 0 then
set theExtension to text (dot + 1) thru -1 of theFileName
return theExtension is in ImageExtensionList
end if
return false
end isImageFileName
When run, I get the error:
error "Mail got an error: Can’t continue isImageFileName." number -1708
where error -1708 is:
Event wasnt handled by an Apple event handler.
However, if I copy/paste the isImageFileName() into another script like:
property ImageExtensionList : {"jpg", "jpeg"}
on isImageFileName(theFileName)
set dot to offset of "." in theFileName
if dot > 0 then
set theExtension to text (dot + 1) thru -1 of theFileName
return theExtension is in ImageExtensionList
end if
return false
end isImageFileName
if isImageFileName("foo.jpg") then
return true
else
return false
end if
it works fine. Why does Mail complain about this?

Answer 1

It may be a quirk, but it has an explanation. If you're in a tell application "whatever" block, all calls are made in the namespace of that application's dictionary, not your script's dictionary. Because of that, you have to explicity tell AppleScript to look back into your script for the name. Saying my is like saying tell me, instructing the script where to look for the function.

Answer 2

Try "my isImageFileName". It's not Mail, just a quirk of AppleScript.