AppleScript: The Definitive Guide, 2nd Edition

File Coercions

The various coercions and other forms of conversion that are and are not possible between a file specifier, a POSIX file (file URL ), an alias , and a string or Unicode text (which might represent a Macintosh pathname or a POSIX pathname), are enough to make your head swim. The trouble is that there are many things you can't do; at the same time, there's always a workaround if you're willing to jump through hoops.

A Macintosh pathname string can be used to form a file specifier or alias. (A file specifier cannot be assigned to a variable or displayed as a result, but a reference to it can be.) A POSIX pathname string can be used to form a POSIX file specifier. (See Chapter 13.) As I pointed out earlier in the chapter, these are not coercions.

An alias can be coerced to a string representing its Macintosh pathname, and its POSIX path property is a string representing its POSIX pathname. An alias cannot be coerced to a file object, but a string can be used as an intermediary to form a file specifier:

set a to alias "gromit:Users:matt2:reason:Resources:"
POSIX path of a -- "/Volumes/gromit/Users/matt2/reason/Resources/"
a as string -- "gromit:Users:matt2:reason:Resources:"
a reference to file (a as string)
-- file "gromit:Users:matt2:reason:Resources:" of «script»

A Macintosh pathname can be coerced to an alias. (The item denoted by the pathname must exist at runtime; see Chapter 13.)

set s to "gromit:Users:matt2:reason:Resources:"
s as alias -- alias "gromit:Users:matt2:reason:Resources:" ...