how to script with Objective-C
Is it me, or is AppleScript experiencing something of an Indian Summer? It seems everywhere I go, people are talking more about macOS automation, AppleScript and even Apple’s curious hybrid syntax AppleScriptObjC (ASObjC).
Of course, some people have suffered miserably at the hands of AppleScript in the past, and even though the thought of scripting with access to Cocoa APIs through Objective-C is tempting, they fear the AppleScript side of it.
If that’s you, bear in mind that AppleScriptObjC isn’t really “AppleScript + Objective-C” at all. It is actually just a dialect of Objective-C that will be accepted in the (Apple)Script Editor and can be run by an instance of the AppleScript component. In plainer English, you can use Objective-C in an AppleScript without any AppleScript whatsoever!
The point of doing so would be that one could package Objective-C code in a .scpt file (or scptd bundle or AppleScript .app), and also mix whatever scripting language you prefer with calls to Cocoa’s APIs.*
The problem that using ASObjC presents anyone familiar with Objective-C is how to translate ‘pure’ Objective-C into the dialect that Script Editor (and other applescript runners like FastScripts, Keyboard Maestro, Automator, etc) can understand. If you use LateNight Software’s Script Debugger for scripting, you’ll already know that the work is done for you by the app’s built-in code completion. If you’re battling on in Apple’s default Script Editor, you’ll need to do the translation manually.
By way of example, then, here’s some original Objective-C, and below it, a translation that would work in Script Editor:
NSString *aString = @"hello";
NSString *bString = @" world";
aString = [aString stringByAppendingString:bString];
NSUserNotification *notif = [[NSUserNotification alloc] init];
notif.informativeText = aString;
[[NSUserNotificationCenter defaultUserNotificationCenter] deliverNotification:notif];
set aString to NSString's stringWithString:"hello"
set bString to NSString's stringWithString:" world"
set aString to aString's stringByAppendingString:bString
set notif to NSUserNotification's alloc's init
set notif's informativeText to aString
NSUserNotificationCenter's defaultUserNotificationCenter()'s deliverNotification:notif
As you can see, there’s a direct 1-to-1 correspondence, with the 6 statements in Objective-C paralleled by the 6 statements in AppleScriptObjC.
The main peculiarity is the use of possessive word forms and that variable attribution is done by using
"set X to Y" rather than
"X = Y". Type declaration is done via the idiom
'set <var> to <NSObject>'s <class init method>', which returns an instance of the object just as it would normally. You call instance methods by putting the instance in front of the method just as you would in regular Objective-C (e.g, see line 3 of the examples).
As you can see in the screenshot below showing Xcode and Script Editor, they work in the same way. You’ll notice in Script Editor there is a
'use' statement (equivalent to Objective-C’s ‘import’), and there’s also a whole load of property statements. These latter are peculiar to the ASObjC translation, and don’t have a counterpart in pure Objective-C. All you need to know about these is for each kind of Objective-C object you want to use (NSString, NSArray, whatever*), you’ll want a property statement for it at the beginning of the script. The statement always has the same form:
property <NSObject> : a reference to current application's < NSObject>
I think the best way to think of ASObjC was recently summed up by Sal Saghoian, when he said that ASObjC is “…the ultimate duct tape. You can do anything you want with ASObjC. You own the computer.”
*not all Cocoa frameworks nor all Objective-C objects can be bridged to, but pretty much all the most useful ones are available.