Kotlin:如何在Joda间隔内迭代所有日期?

深受您当前解决方案的启发:

fun Interval.toDateTimes() = generateSequence(start) { it.plusDays(1) }
                                                 .takeWhile(::contains) 

interval.toDateTimes()
        .forEach { println(it) }

如果你需要 LocalDate 您仍然可以执行以下操作:

interval.toDateTimes()
        .map(DateTime::toLocalDate)
        .forEach { println(it) }

Interval 再一次:

fun Interval.toLocalDates() = toDateTimes().map(DateTime::toLocalDate)

如果希望结束日期包含在内,请使用 takeWhile { it <= end }

下面的扩展函数给出 Sequence 属于 LocalDate 来自给定 Interval ,可用于迭代这些日期。

fun Interval.toLocalDates(): Sequence<LocalDate> = generateSequence(start) { d ->
    d.plusDays(1).takeIf { it < end }
}.map(DateTime::toLocalDate)

用法:

val interval = Interval(DateTime.now().minusDays(42), DateTime.now())
interval.toLocalDates().forEach {
    println(it)
}

在这个解决方案中,最后一天, DateTime.now() 顺序 间隔 也实施了:

“时间间隔表示两个瞬间之间的一段时间。间隔包括开始时刻,不包括结束时刻。”

如果出于任何原因,你想让它包括最后一天,只需更改 takeIf 条件到 it <= end .

for (i in LocalDate.now() .. LocalDate.now().plusWeeks(1)) {
    System.out.print(i) // 2018-08-30 2018-08-31 2018-09-01 
}

以下是操作员分机代码:

operator fun LocalDate.rangeTo(other: LocalDate): LocalDateRange {
    return LocalDateRange(this, other)
}

class LocalDateRange(override val start: LocalDate, override val endInclusive: LocalDate)
    : ClosedRange<LocalDate>, Iterable<LocalDate> {
    override fun iterator(): Iterator<LocalDate> {
        return DateIterator(start, endInclusive)
    }
}

class DateIterator(start: LocalDate, private val endInclusive: LocalDate)
    : Iterator<LocalDate> {

    private var current = start

    override fun hasNext(): Boolean {
        return current <= endInclusive
    }

    override fun next(): LocalDate {
        current = current.plusDays(1)
        return current
    }
}

LocalDate 是现在的首选,所以我们可以简单地以天作为数字进行迭代:

for (day in minDate.toEpochDay()..maxDate.toEpochDay()) {
    // ...
}

或:

(minDate.toEpochDay()..maxDate.toEpochDay()).forEach {
    // ...
}

generateSequence(minDate) { it.plusDays(1) }.takeWhile { it < maxDate }.forEach {
    // it ...
}

或:

var day = minDate;
while (day < maxDate) {
    day = day.plusDays(1);
    // ...
}