swift - 如何计算 Swift 中的特定日期(使用 NSDate)

Question

我正在使用 swift 开发 ios 应用程序，我有一个带有 7 个选项的 slider 。每个选项代表特定日期。

目前我的代码如下:

func convertValueToDate(value: Float) -> NSDate{

    var currentDate:NSDate = NSDate()

    switch(value){
    case 1:
        print("5 years ago")
        return NSDate()
    case 2:
        print("one year ago")
        return NSDate()
    case 3:
        print("six months ago")
        return NSDate()
    case 4:
        print("one month ago")
        return NSDate()
    case 5:
        print("one week ago")
        return NSDate()
    case 6:
        print("yesterday")
        return NSDate()
    case 7:
        print("today")
        return NSDate()
    default:
        print("default date")
        return NSDate()
    }
}

正如您在上面看到的那样 - 我在控制台中打印了我想要返回的内容。但我不想打印，而是想以 NSDate 格式返回这些日期。我不知道如何计算每个选项的时间，因为我想每天都有 0:00:01 AM 的时间。所以例如。当用户输入数字 7 时，我想向他返回昨天 0:00:01 AM 的确切日期。当用户选择数字 5 时，我想给他一个星期前的日期，时间为 0:00:01 AM，依此类推。我如何计算它以便此函数始终返回时间 0:00:01 AM 和计算日期？

Answer 1

您可以使用 NSCalendar 方法 dateByAddingUnit:

func convertValueToDate(value: Float) -> NSDate {
    struct Cal {
        static let iso8601 = NSCalendar(identifier: NSCalendarIdentifierISO8601)!
    }
    let now = NSDate()
    print("now: ", now)
    switch(value) {
    case 1:
        print("5 years ago")
        return Cal.iso8601.dateByAddingUnit(.Year, value: -5, toDate: now, options: [])!
    case 2:
        print("one year ago")
        return Cal.iso8601.dateByAddingUnit(.Year, value: -1, toDate: now, options: [])!
    case 3:
        print("six months ago")
        return Cal.iso8601.dateByAddingUnit(.Month, value: -6, toDate: now, options: [])!
    case 4:
        print("one month ago")
        return Cal.iso8601.dateByAddingUnit(.Month, value: -1, toDate: now, options: [])!
    case 5:
        print("one week ago")
        return Cal.iso8601.dateByAddingUnit(.WeekOfYear, value: -1, toDate: now, options: [])!
    case 6:
        print("yesterday")
        return Cal.iso8601.dateByAddingUnit(.Day, value: -1, toDate: now, options: [])!
    case 7:
        print("today")
        return now
    default:
        print("default date")
        return now
    }
}

如果您需要返回该日期的开始日期，您可以使用 NSCalendar startOfDayForDate 方法。

func convertValueToDate(value: Float) -> NSDate {
    struct Cal {
        static let iso8601 = NSCalendar(identifier: NSCalendarIdentifierISO8601)!
    }
    let now = NSDate()
    print("now: ", now)
    let result: NSDate
    switch(value) {
    case 1:
        print("5 years ago")
        result = Cal.iso8601.dateByAddingUnit(.Year, value: -5, toDate: now, options: [])!
    case 2:
        print("one year ago")
        result =  Cal.iso8601.dateByAddingUnit(.Year, value: -1, toDate: now, options: [])!
    case 3:
        print("six months ago")
        result =  Cal.iso8601.dateByAddingUnit(.Month, value: -6, toDate: now, options: [])!
    case 4:
        print("one month ago")
        result =  Cal.iso8601.dateByAddingUnit(.Month, value: -1, toDate: now, options: [])!
    case 5:
        print("one week ago")
        result =  Cal.iso8601.dateByAddingUnit(.WeekOfYear, value: -1, toDate: now, options: [])!
    case 6:
        print("yesterday")
        result =  Cal.iso8601.dateByAddingUnit(.Day, value: -1, toDate: now, options: [])!
    case 7:
        print("today")
        result = now
    default:
        print("default date")
        result = now
    }
    return Cal.iso8601.startOfDayForDate(result)
}