func parseDuration(timeString:String) -> NSTimeInterval {
    guard !timeString.isEmpty else {
        return 0
    }

    var interval:Double = 0

    let parts = timeString.componentsSeparatedByString(":")
    for (index,part) in parts.reverse().enumerate() {
        interval += (Double(part) ?? 0) * pow(Double(60),Double(index))
    }

    return interval
}

它适用于像二时12分12秒,02：01：23.123213