String+Range.swift

extension String {
    func rangeFromNSRange(nsrange:NSRange) -> Range<String.Index> {
        let string = self
        let startIndex = string.startIndex.advancedBy(nsrange.location)
        let endIndex = startIndex.advancedBy(nsrange.length)
        let range = Range(start:startIndex, end:endIndex)
        return range
    }
    func NSRangeFromRange(range:Range<String.Index>) -> NSRange {
        let location = self.startIndex.distanceTo(range.startIndex)
        var length = 0
        var index = range.startIndex
        while index < range.endIndex {
            length += 1
            index = index.successor()
        }
        return NSMakeRange(location, length)
    }
}