swift - NSDateFormatter 给我一周中不同的两天，同一日期

Question

有很多约会，我正在尝试获取他们一周中的哪几天。但每当我循环浏览时，即使在午夜之后，一周中的日子也有几个小时没有改变，我不知道为什么。这是我的代码:

func parseArray(array: [HKQuantitySample])
{
let formatter = NSDateFormatter()
formatter.dateFormat = "EEEE"

for element in array
{
    let startDate: NSDate = element.startDate //example: 2015-11-13 13:30:07 +0000

    let startDateArray = String(startDate).componentsSeparatedByString(" ") // example: ["2015-11-13", "13:46:53", "+0000"]

    let startDateString = startDateArray[0] // example: 2015-11-13
    let startDateTimeString = startDateArray[1] // example: 13:58:39

    let startDateDayOfTheWeek = formatter.stringFromDate(startDate)

    print("startDate: \(startDateString), startTime: \(startDateTimeString), dayOfWeek: \(startDateDayOfTheWeek)")
}

这是我得到的:

startDate: 2015-11-12, startTime: 23:32:01, dayOfWeek: Thursday
startDate: 2015-11-12, startTime: 23:41:19, dayOfWeek: Thursday
startDate: 2015-11-12, startTime: 23:50:36, dayOfWeek: Thursday

/* 午夜 */

startDate: 2015-11-13, startTime: 00:07:35, dayOfWeek: Thursday
startDate: 2015-11-13, startTime: 00:19:19, dayOfWeek: Thursday
startDate: 2015-11-13, startTime: 00:32:20, dayOfWeek: Thursday
startDate: 2015-11-13, startTime: 00:41:37, dayOfWeek: Thursday
startDate: 2015-11-13, startTime: 00:55:34, dayOfWeek: Thursday
startDate: 2015-11-13, startTime: 01:04:51, dayOfWeek: Thursday
2016-06-21 17:39:10.446213 appleWatchHealth[1173:238873] [MC] Reading from public effective user settings.
startDate: 2015-11-13, startTime: 01:14:57, dayOfWeek: Thursday
startDate: 2015-11-13, startTime: 01:24:50, dayOfWeek: Thursday
startDate: 2015-11-13, startTime: 01:36:39, dayOfWeek: Thursday
startDate: 2015-11-13, startTime: 01:45:56, dayOfWeek: Thursday

所以即使从 12 号变成了 13 号，它仍然给我星期四。不过，它确实更改为周五下午 1 点左右:

startDate: 2015-11-13, startTime: 13:01:31, dayOfWeek: Friday

另外，我不知道最后一行是什么意思:

2016-06-21 17:39:10.446213 appleWatchHealth[1173:238873] [MC] Reading from public effective user settings.

Answer 1

String(startDate)使用startDate的描述，纯粹是为了调试目的。您永远不应该将其用于最终用户看到的东西。因此，没有办法让它显示除您所看到的内容之外的任何内容。

每当您想要将 NSDate 转换为最终用户看到的内容时，都应该使用 NSDateFormatter。