1.3. Calculation and Repetition

Computers are good at calculation and repetition . Humans, on the other hand, are liable to calculate inaccurately, and all the more so in the face of repetitive activity, which can make them careless, bored, and angry. Calculation and repetition on a computer should be performed by the computernot by a human.

Here's an example straight off the Internet, where someone writes: "I want to rename a whole lot of image files based on the names of the folders they're in." One's eyes glaze over at the prospect of doing this by hand. Yet with AppleScript, it's a snap. The task would make a good dropleta little application, written with AppleScript, with a Finder icon onto which you can drop files and folders you want processed. (More details appear in "Applet and Droplet" in Chapter 3 and "Applets" in Chapter 27.) Here's the AppleScript code for such a droplet; you drop a folder or folders onto its icon in the Finder, and it renames all items in each folder using that folder's name followed by a number:

on open folderList
    repeat with aFolder in folderList
        if kind of (info for aFolder) is "Folder" then
            renameStuffIn(aFolder)
        end if
    end repeat
end open
on renameStuffIn(theFolder)
    set ix to 0
    tell application "Finder"
        set folderName to name of theFolder
        set allItems to (get every item of theFolder)
        repeat with thisItem in allItems
            set ix to ix + 1
            set newName to folderName & ix
            set name of thisItem to newName
        end repeat
    end tell
end renameStuffIn

The parameter folderList tells us what was dropped onto the droplet. We process each dropped item, starting with a sanity check to make sure it's really a folder. If it is, we give each item in the folder a new name based on the folder's name along with a number that increases each time.