例えば、String <-> NSAttributedString

ruby>>
@objc(S2ASTransformer) class
S2ASTransformer : NSValueTransformer {

override static	func
transformedValueClass() -> AnyClass {
	return NSAttributedString.self
}
override static	func
allowsReverseTransformation() -> Bool {
	return true
}
override func
transformedValue( p: AnyObject? ) -> AnyObject {
	if let w = p as? String { return NSAttributedString( string: w ) } else { return NSAttributedString() }
}
override func
reverseTransformedValue( p: AnyObject? ) -> AnyObject {
	if let w = p as? NSAttributedString { return w.string } else { return "" }
}

}

<<--

こんなの作ってこうやって登録

ruby>>
func
applicationDidFinishLaunching( p: NSNotification ) {
NSValueTransformer.setValueTransformer( S2ASTransformer(), forName: "S2ASTransformer" )
}

<<--