ios - 无法形成范围与 upperBound < lowerBound

Question

我正在尝试从如下所示的服务器响应中获取日期:

"dateStart": "2019-08-21T14:54:03.285108Z",

"dateEnd": "2019-09-20T06:15:03.285108Z"

因为我只需要日期和月份，所以结果将是:“08-21”和“09-20”

我确实尝试过过滤结果，但我遇到了崩溃:

Thread 1: Fatal error: Can't form Range with upperBound < lowerBound

这是我的代码:

    let startTime = dealStatus["dateStart"] as? String
    let startFirst = startTime!.index(startTime!.startIndex, offsetBy: 5)
    let endFirst = startTime!.index(startTime!.endIndex, offsetBy: -17)
    let startTimeString = startTime![startFirst..<endFirst] // Getting crash here

    let endTime = dealStatus["dateEnd"] as? String
    let startSecond = endTime!.index(endTime!.startIndex, offsetBy: 5)
    let endSecond = endTime!.index(endTime!.endIndex, offsetBy: -17)
    let endTimeString = endTime![startSecond..<endSecond]

    let startReplaced = startTimeString.replacingOccurrences(of: "-", with: ".")
    let endReplaced = endTimeString.replacingOccurrences(of: "-", with: ".")
    let startEndDates = "(" + String(startReplaced) + " - " + String(endReplaced) + ")"
    //
    let orderTitle = ordersResponseArray[indexPath.row]
    let catTitle = orderTitle["title"] as? String
     cell.titleAndDatesLabel.text = catTitle! + " " + startEndDates

如有任何帮助，我们将不胜感激!

Answer 1

您应该首先使用 DateFormatter 或 ISO8601DateFormatter 将 UTC 时间的日期字符串解析为日期对象，并从生成的日期中获取月和日表示形式:

extension Formatter {
    static let monthDay: DateFormatter = {
        let dateFormatter = DateFormatter()
        dateFormatter.locale = Locale(identifier: "en_US_POSIX")
        dateFormatter.dateFormat = "MM.dd"
        return dateFormatter
    }()
}

---

extension Formatter {
    static let iso8601: DateFormatter = {
        let formatter = DateFormatter()
        formatter.calendar = Calendar(identifier: .iso8601)
        formatter.locale = Locale(identifier: "en_US_POSIX")
        formatter.timeZone = TimeZone(secondsFromGMT: 0)
        formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSSXXXXX"
        return formatter
    }()
}

---

Playground 测试:

let dealStatus: [String: Any] = ["dateStart": "2019-08-21T14:54:03.285108Z",
                                 "dateEnd"  : "2019-09-20T06:15:03.285108Z"]

if let dateStart = dealStatus["dateStart"] as? String,
    let dateEnd = dealStatus["dateEnd"] as? String,
    let start = Formatter.iso8601.date(from: dateStart),
    let end = Formatter.iso8601.date(from: dateEnd) { // ,
//  let catTitle = ordersResponseArray[indexPath.row]["title"] as? String {

    let startTime = Formatter.monthDay.string(from: start)
    let endTime = Formatter.monthDay.string(from: end)
    let startEndDates = "(" + startTime + " - " + endTime + ")"
    print(startEndDates)  // "(08.21 - 09.20)"
    //    cell.titleAndDatesLabel.text = catTitle + " " + startEndDates
}