class NSButton
{
	// Swizzle an instance method of an existing class
	Swizzle- (void)drawRect:(NSRect)rect
	{
	    // Draw something behind the button
	    ...
	    // Call original swizzled method, this will call NSButton's drawRect:
	    this.Original(arguments)
	    // Draw something in front of the button
	    NSBezierPath.bezierPathWithOvalInRect(rect).stroke
	}
}

swizzling is replacing a method's implementation with our own. This example swizzles NSButton's drawRect: with a Javascript function : each time a button must be drawn, the ObjC runtime will call this Javascript function. If you want to modify the behaviour of existing classes without deriving, swizzling is the way to go ! Thanks to JRSwizzle for the code.

Add Swizzle in front of a method definition to swizzle it. To call the original method, call this.Original(arguments).

// JSTalk-enable your application
[JSTalk listen];

// From the JSTalk editor you can then script it in Javascript
var sketch = JSTalk.application("Sketch");
var doc = sketch.orderedDocuments()[0];
var rectangle = doc.makeNewBox();
rectangle.setWidth(100);
rectangle.setHeight(100);

// Or use an ObjC syntax
var bezierPath = [NSBezierPath bezierPath];
[bezierPath curveToPoint:pointA controlPoint1:pointB controlPoint2:pointC];
[bezierPath fill];

// Check if getting property is allowed
- (BOOL) JSCocoa:(JSCocoaController*)controller canGetProperty:(NSString*)propertyName ofObject:(id)object inContext:(JSContextRef)ctx exception:(JSValueRef*)exception;
// Custom handler for getting properties
//	Return a custom JSValueRef to bypass JSCocoa
//	Return NULL to let JSCocoa handle getProperty
//	Return JSValueMakeNull() to return a Javascript null
- (JSValueRef) JSCocoa:(JSCocoaController*)controller getProperty:(NSString*)propertyName ofObject:(id)object inContext:(JSContextRef)ctx exception:(JSValueRef*)exception;

After restricting access with the can* methods, you can use getProperty, setProperty, callMethod to bypass JSCocoa and implement custom behaviour to return custom values to Javascript.

canLoadJSFile, canEvaluateScript restrict script loading. willEvaluateScript gives you a change to transform the input script before evaluation : use it to implement a custom syntax or expand your own macros.

	// Define a new class
	class MyClass < NSObject
	{
		// instance method
		- (int)addX:(int)x andY:(int)y
		{
			return x + y
		}
		// class method
		+ (float)addFloatX:(float)x andFloatY:(float)y
		{
			return x + y
		}

		// Interface Builder outlet		
		IBOutlet outlet1
		// Interface Builder outlet using a Javacript notification
		IBOutlet outlet2 (newValue)
		{
			log('new value of outlet2=' + newValue)
		}

		// Interface Builder action, using sender as default parameter
		IBAction clickMe
		{
			log('Button clicked=' + sender)
		}
		// Interface Builder action, using custom parameter name
		IBAction clickMeToo(notifier)
		{
			log('Button clicked=' + notifier)
		}
	}

	// Functions like NSOpenGLGetVersion(int*, int*) expect two pointers to int
	// JSCocoa detects pointer types and auto allocs required size
	var major = new outArgument
	var minor = new outArgument
	NSOpenGLGetVersion(major, minor)
	log('OpenGL version : ' + major + '.' + minor)

	// Using with structures
	var rect = new NSRect(10, 20, 30, 40)
	var rect1 = new outArgument
	var rect2 = new outArgument

	NSDivideRect(rect, rect1, rect2, 5, NSMinXEdge)
	log('Divided rect1=' + rect1)

	// Using with ObjC methods : scanning a string with NSScanner
	var scanner = NSScanner.scannerWithString('4.56 123')
	var extractedFloat = new outArgument
	scanner.scanFloat(extractedFloat)
	log('extracted=' + extractedFloat)

	// 
	// Memory buffers : manually allocating memory and using it as data source or sink
	// 

	// Data source : copy color components into our buffer
	// Allocate room for 4 floats
	var buffer = new memoryBuffer('ffff')

	// Extract components of a NSColor into our buffer
	color.get({	red : new outArgument(buffer, 0), 
			green : new outArgument(buffer, 1), 
			blue : new outArgument(buffer, 2),
			alpha : new outArgument(buffer, 3) })
	log('Extracted red=' + buffer[0])

	// Data sink : copy point coordinates into a NSBezierPath element
	// Allocate room for 3 points
	var buffer = new memoryBuffer('ffffff')
	// Set new point values
	buffer[0] = 10.0
	buffer[1] = 5.0
	...
	...

	// Fill a NSBezierPath element with our new coordinates
	path.setAssociatedPoints_atIndex(buffer, 1)

• Create an iPhone app and classes in ObjC then use JSCocoa to script these classes
• Create dummy derived classes with dummy methods each calling their Javascript counterpart
• Somehow make mprotect work

I love Git, it's really a "what's changed" manager for directories used as source control. Files referenced once will exist only once, files moved will keep refering to the same object, and it's easy to use :
git add . to add the current directory,
git commit -a -m "new version!"; git push to send the new version to Github.
You can tag releases, easily branch from them, all of that locally !