Swift String : rangesOf substrings

rangesOfSubstrings.swift

extension String {
    func ranges(of subString: String) -> [NSRange] {
        var result: [NSRange] = []
        var start = startIndex
        while let range = range(of: subString, options: .literal, range: start..<endIndex) {
            let startPos = self.distance(from: self.startIndex, to: range.lowerBound)
            let endPos = self.distance(from: self.startIndex, to: range.upperBound)
            result.append(NSMakeRange(startPos, (endPos - startPos)))
            start = range.upperBound
        }
        return result
    }
}