Find all locations of substring in NSString

Find all locations of substring in NSString

extension NSString {
    func rangesOfSubString(_ string: String) -> [NSRange] {
        var searchRange = NSMakeRange(0, length)
        var searchResult = [NSRange]()
        while searchRange.location < length {
            searchRange.length = length - searchRange.location
            let foundRange = range(of: string, options: [], range: searchRange)
            if foundRange.location != NSNotFound {
                searchResult.append(foundRange)
                searchRange.location = foundRange.location+foundRange.length
            } else {
                break
            }
        }
        return searchResult
    }
}