ios - 从 (NSDate) -> NSTimeInterval 转换为不相关的类型 'NSTimeInterval 总是失败

Question

我试图找出从我的 iPad 到我的网站的时间差异，它们都是本地的。一切正常，直到我到达下面的行，它应该占用 iPad 时间并从中减去 serverTime。

self.serverTimeOffSet = NSDate.timeIntervalSinceDate(serverTime) as NSTimeInterval

我收到警告“Cast from (NSDate) -> NSTimeInterval to unrelated type 'NSTimeInterval always fails”并且 self.serverTimeOffset 从未设置。

var serverTimeOffSet: NSTimeInterval = 0.0

func setServerOffset(){
    var currentTime = NSDate.timeIntervalSinceReferenceDate()
    var url = NSURL(string: "http://someurl.com/time")
    var request = NSMutableURLRequest(URL:url!)
    var response: NSURLResponse?
    var error: NSError?
    request.HTTPMethod = "get"
    request.setValue("application/json", forHTTPHeaderField: "Content-Type")
    NSURLConnection.sendAsynchronousRequest(request, queue: NSOperationQueue.mainQueue(), completionHandler: {(response:NSURLResponse!, data:NSData!, error:NSError!) -> Void in
        if (error == nil) {
            var dateString = NSString(data: data, encoding: NSUTF8StringEncoding) as! String
            let dateFormatter = NSDateFormatter()
            dateFormatter.dateFormat = "YYYY-MM-dd'T'HH:mm:ss"
            dateFormatter.locale = NSLocale(localeIdentifier: "en_US_POSIX")
            if let serverTime = dateFormatter.dateFromString(dateString){
                self.serverTimeOffSet = NSDate.timeIntervalSinceDate(serverTime) as NSTimeInterval
            }
        }
    })
}

谢谢

编辑 - 从站点返回的日期:

2015-09-15T00:01:44.8530546-06:00

Answer 1

您还应该按如下方式格式化您的日期:

let dateString = "2015-09-15T00:01:44.8530546-06:00"
let dateFormatter = NSDateFormatter()
dateFormatter.calendar = NSCalendar(calendarIdentifier: NSCalendarIdentifierISO8601)
dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSSSSSSxxx"
dateFormatter.locale = NSLocale(localeIdentifier: "en_US_POSIX")
if let serverTime = dateFormatter.dateFromString(dateString){
   serverTime  // "Sep 15, 2015, 3:01 AM"
}