以下解决方案使用本机Swift 4函数range(of:, options:, range:, locale:)):

The following solution uses the native Swift 4 function range(of:, options:, range:, locale:)):

extension String {
    func ranges(of substring: String, options: CompareOptions = [], locale: Locale? = nil) -> [Range<Index>] {
        var ranges: [Range<Index>] = []
        while ranges.last.map({ $0.upperBound < self.endIndex }) ?? true,
            let range = self.range(of: substring, options: options, range: (ranges.last?.upperBound ?? self.startIndex)..<self.endIndex, locale: locale)
        {
            ranges.append(range)
        }
        return ranges
    }
}

(然后Swift 4提供了本机API，可以从Range<Index>转换为NSRange)

(Swift 4 then provides native API to convert from Range<Index> to NSRange)