Question

我试图理解NSCalendar及其组件在Swift中的工作原理。我从日期中提取了组件，更改了组件属性，并重新构建了日期。我期待得到Sept 9, 2015, 12:00 AM但是取而代之的是Sept 9, 2015, 8:00 AM。

为什么小时组件是在上午8:00？

let calendar = NSCalendar(calendarIdentifier: NSCalendarIdentifierGregorian)
calendar?.timeZone = NSTimeZone(abbreviation: "GMT")!

let components = calendar?.components([.Year, .Month, .Day, .Hour, .Minute, .Second], fromDate: NSDate())

components?.year            // 2016
components?.month        // 9
components?.day            // 9
components?.hour          // 4
components?.minute      // 31
components?.second      // 54

components?.year = 2015
components?.month = 9
components?.day = 9
components?.hour = 0
components?.minute = 0
components?.second = 0

calendar?.dateFromComponents(components!) // Sept 9, 2015, 8:00 AM

上面的代码不适用于任何用例。我只想了解NSCalendar，NSDateComponents和NSDate是如何联系在一起的。

Answer 1

当您打印它时，您将获得正确的日期，NSDate为Sept 9, 2015, 8:00 AM是因为您将时区设置为GMT，如果您将时区更改为{，则会将日期返回为"Sep 9, 2015, 12:00 AM" {1}}

dateFromComponents默认为上午8:00

1 个答案: