swift - 如何以给定的粒度生成两个日期之间的每个日期？

Question

如何以给定的粒度生成两个日期之间的每个日期？

我想让这个扩展板成为一个日期数组，所有日期都必须在 00 米、15 米、30 米或 45 米处，这样就没有间隙。 (可选)设置开始日期和结束日期，它们不在原始集合中(因此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 */]

如果它像 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，直到新日期应该大于结束日期

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 }
    }

}