gistfile1.swift

import UIKit

extension String {
    func NSRangeOfString(string: String) -> NSRange? {

        if let range = self.rangeOfString(string) {
            let loc = distance(self.startIndex, range.startIndex)
            let length = distance(range.startIndex, range.endIndex)
            
            return NSMakeRange(loc, length)
            
        } else {
            return nil
        }
    }
}


let hello = "Hëllø Wœrld!"
let cjk   = "Christian"


// Using an ASCII string. The metrics compared to the unicodian multi-byte string
// should be the same, because of the same amount of graphemes.

let formattedHello = NSMutableAttributedString(string: "Hello World and others!")


if let range = hello.NSRangeOfString("Wœrld") {
    
    formattedHello.addAttribute(NSForegroundColorAttributeName,
                                value: UIColor.redColor(),
                                range: range)
    
    formattedHello.replaceCharactersInRange(range, withString: cjk)

}