比较NSDate

Question

我想比较两个NSDates,但每个日期显示为"早于" 今天的日期.有任何想法吗？

let compareResult = self.todaysDate.compare(self.date)

if compareResult == NSComparisonResult.OrderedDescending {
println("Today is later than date2")
} else {
println("Future")
}

获得"今日日期"

let todaysDate = NSDate()
let calendar = NSCalendar.currentCalendar()
    let components = calendar.components(.CalendarUnitHour | .CalendarUnitMinute | .CalendarUnitMonth | .CalendarUnitYear | .CalendarUnitDay, fromDate: todaysDate)
let hour = components.hour
let minutes = components.minute
let month = components.month
let year = components.year
let day = components.day
println(todaysDate)

这个印刷品是:

2014-11-12 14:48:48 +0000

而"日期"的印刷品是:

2014-10-24 07:24:41 +0000

这是在Parse.com服务器上.

谢谢

Answer 1

我想也许你正在解释compare倒退的结果.看一下这个.每个asserts通行证:

let today = NSDate()
let tomorrow = today.dateByAddingTimeInterval(24 * 60 * 60)
let yesterday = today.dateByAddingTimeInterval(-24 * 60 * 60)

assert(today.compare(tomorrow)  == .OrderedAscending)     // today < tomorrow
assert(today.compare(yesterday) == .OrderedDescending)    // today > yesterday
assert(today.compare(today)     == .OrderedSame)          // today == today

Answer 2

如果你想支持==,<,>,<=,或>=为NSDateS,你只需要声明这个地方:

public func ==(lhs: NSDate, rhs: NSDate) -> Bool {
    return lhs === rhs || lhs.compare(rhs) == .OrderedSame
}

public func <(lhs: NSDate, rhs: NSDate) -> Bool {
    return lhs.compare(rhs) == .OrderedAscending
}

extension NSDate: Comparable { }

实施==和<允许Comparable推断出其他比较操作.

用法:

let date1 = NSDate()
let date2 = NSDate()

println(date2 > date1) // true
println(date2 < date1) // false
println(date2 == date2) // true