如何将两个日期之间的每个日期生成到给定的粒度

Question

如何将两个日期之间的每个日期生成到给定的粒度？

我想使这个扩展垫成为日期数组，它们都必须在 00m、15m、30m 或 45m 处，这样就不会有间隙。（可选）设置不在原始集中的开始日期和结束日期（以便您可以有前导日期和尾随日期）。

extension TimeSeries {
    var earliest: Date? {
        return timeSeries.map { $0.date }.min()
    }
    var latest: Date? {
        return timeSeries.map { $0.date }.max()
    }
    func pad (to repletion: Int, _ component: Calendar.Component, from: Date? = nil, to: Date? = nil) {
        guard let start = from ?? self.earliest else {
            print("no start date given and none available")
            return
        }
        guard let end = to ?? self.latest else {
            print("no end date given and none available")
            return
        }
        // magic happens here...
    }
}

具体来说，给定：

[ Date/* 2018-01-16 01:15:00 */, Date/* 2018-01-16 01:45:00 */]

我希望数组变成：

[ Date/* 2018-01-16 01:15:00 */,  Date/* 2018-01-16 01:30:00 */, Date/* 2018-01-16 01:45:00 */]

如果它被称为ts.pad(to: 15, .minutes, from: Date/* 2018-01-16 01:00:00 */, to: Date/* 2018-01-16 02:00:00 */ )

我希望数组变成：

[ Date/* 2018-01-16 01:00:00 */, Date/* 2018-01-16 01:15:00 */,  Date/* 2018-01-16 01:30:00 */, Date/* 2018-01-16 01:45:00 */, Date/* 2018-01-16 02:00:00 */]

Answer 1

逻辑可能是这样的。创建以开始日期作为第一个元素的数组。然后将添加组件的日期附加到最后一个日期，直到新日期应大于结束日期

func pad(to repletion: Int, _ component: Calendar.Component, from: Date? = nil, to: Date? = nil) {
    guard let start = from ?? self.earliest, let end = to ?? self.latest else {
        print("no date given and none available")
        return
    }
    var components = DateComponents()
    components.setValue(repletion, for: component)
    let calendar = Calendar.current
    var dates = [start] // results
    while start < end {
        if let newDate = calendar.date(byAdding: components, to: dates.last!), 
           newDate <= end {
            dates.append(newDate)
        } else { break }
    }
}

Answer 2

这是我

的变体，假设周期由start和end日期给出

let quarter: TimeInterval = 15 * 60
let dateInterval = DateInterval(start: start, end: end)
var date = start
var result = [Date]()
while dateInterval.contains(date) {
    result.append(date)
    date = date.addingTimeInterval(quarter)
}