With all the excitement over Mavericks’ fancy new apps, memory compression and Finder enhancements, perhaps one of the most revolutionary changes to go largely unnoticed is to the venerable (yes, it’s 20 years old, this year!) programming language AppleScript.

Apple have quietly introduced a new command to the AppleScript language called ‘use’. In effect, ‘use’ replicates the preprocessor ‘import’ directive familiar to Objective C users or the ‘include’ directive known to C programmers. This is likely to have a radical effect on how people learn and write AppleScripts.

Although ‘use’ seems primarily intended as a means to turbo-boost AppleScript by making available Objective C methods to scripters, it can also be used to import the scripting language of any app on your system. With that power, the whole concept (and limitations) of the ‘tell’ block are done away with. To see how this works in practice, take a look at this short script for toggling Bluetooth depending on your power source that I wrote pre-Mavericks, using tell statements and blocks:

Compare that with how we will do it now in 10.9 with the ‘use’ statement*:

Not a ‘tell’ in sight! Note the three ‘use’ declarations at the beginning of the script. The first one tells the script editor to include terms from System Events scripting dictionary. The second one does something similar with terms from System Preferences, but you’ll notice the syntax is slightly different. In the second declaration, I’ve taken advantage of the optional means to define a global text substitution for the expression “application System Preferences”. If you’re familiar with the #define directive in Objective C, or with using global properties in AppleScript of old, you’ll understand how this works. If you’re not, the short version is that we’ve declared a global variable of the sort which allows us to use the expression SysPrefs wherever we would normally have used the string application "System Preferences".

Don’t overlook the third ‘use’ statement in my example script above. Using ‘use’ effectively disables scripting additions (that includes all your familiar ‘display dialog’, ‘clipboard’, ‘path to’ and other essential expressions). In short, if you include any ‘use’ statements, be sure to also add the ‘use scripting additions’ statement, too.

There’s a lot more to using ‘use’ (you can read the full documentation here), but overall I think this is a positive change. However, if you’re fond of ‘tell’ don’t despair. At least for now, there’s no sign that ‘tell’ is being deprecated and you can carry on using it just as before.

🙂

*Note that there are other changes in the Mavericks version of the Bluetooth toggle script (in the ‘if…else’ blocks) due to the fact that Mavericks has changed the Bluetooth system prefs pane.