String.rangeofString to NSRange

String+NSRangeOfString.swift

extension String {
    func NSRangeOfString(string: String) -> NSRange {
        let range = self.rangeOfString(string)
        if (range != nil) {
            let first: Int = self.startIndex.distanceTo(range!.startIndex)
            let length: Int = range!.startIndex.distanceTo(range!.endIndex)
            return NSMakeRange(first, length)
        }
        return NSMakeRange(NSNotFound, 0)
    }
}