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Creating a file object from an HFS string

I'm learning AppleScript from various online articles and yt tutorials and I've come a cropper over the whole Files and Alias topic.

According to this guide, (listing 15.8) I should be able to create a file object with the line

set theFile to file "Macintosh HD:Users:yourUserName:Desktop:My File.txt"

This throws up an error

Script Editor error

I've done a lot of googling and only found one reference to the issue:

Oddly, you can't assign a file object specifier to a variable, or return it as a value. If you try, you get a runtime error message:

set x to file "feathers:Users:mattneub:"
-- error: Can't make file "feathers:Users:mattneub:" into type reference

Instead, you must generate a reference to the file object, like this:

set x to a reference to file "feathers:Users:mattneub:"
x -- file "feathers:Users:mattneub:" of «script»

In the AppleScript Language Guide a file object is created via the pseudo class POSIX file

Working With Files
AppleScript uses file objects to represent files in scripts. A file object can be stored in a variable and used throughout a script. The following script first creates a file object for an existing file in the variable notesFile, then uses the variable in a tell statement that opens the file:

set notesFile to POSIX file "/Users/myUser/Feb_Meeting_Notes.rtf"
tell application "TextEdit" to open notesFile

I find this bizarre!

As I understand it, file paths inside the file object are stored as HFS, so should I want to create a file object from an HFS string, I need to

  • create a POSIX path from the HFS string
  • put the POSIX path through POSIX file

which returns a file object with the path stored as an HFS string again!

(Although apparently POSIX file doesn't even output a file object, but a file URL?!)

My question in short: Why can't I set a variable as a file object by appending file to an HFS string as in the listing 15.8 quoted above? Do I always have to go via POSIX path and POSIX file?.

I'm wondering if the code does actually work, just not on its own? I haven't actually got as far as to work out why I need or how to use file objects, so my understanding could be patchy...

In a tutorial about converting between POSIX and HFS paths, and aliases, I decided to try and convert an alias to a file object and opened this can of worms.

Any help is much appreciated, even if the answer is: you'd never need to do this, so just ignore it! 😅

Solution

  • Here you do not understand what the manuals explain. Listing 15.8 shows exactly the wrong attempt to create a file reference using old type file specifier (file). This specifier is left over from the past to work with AppleScript commands such as read and write.

    The manual clearly shows the correct creation of the old type file reference (file) from HFS path:

    set theFile to a reference to file "Macintosh HD:Users:yourUserName:Desktop:My File.txt"

    Later, you can use this reference any time with AppleScript commands read and write. For example:

    read theFile

    Also, the manual clearly states that it is additionally possible to use the read or write command without first creating a separate file reference (variable theFile in your case). So to speak, to read or write "on the fly":

    read file "Macintosh HD:Users:yourUserName:Desktop:My File.txt"