Question

我有一个对象列表

data class OldFormat(ShiftId: Int, NozzleValue: Int, NozzleId: Int , UserId: Int)

我要按两个字段“ shiftId和userId”进行分组，然后从同一组的最小值中减去每个组的最大值，然后对结果求和，然后将其转换为具有此类的新对象：

data class NewFormat(ShiftId: Int, NozzleValue: Int, UserId: Int)

过程如下：

listOfOldFormat -> groupby(shiftId, userId) -> sum(maximumValue-minimumValue) -> listOfNewFormat

Answer 1

我们确实具有groupBy函数，因此我们拥有所需的一切。

我不确定subtract the maximum value of each group from the minimum value of the same group and then sum the result是什么意思（我应该总结什么？），所以我以group.value.max - group.value.min的名字来做，而nozzeValue是NewFormat的意思。 / p>

代码段：

data class OldFormat(val shiftId: Int, val nozzleValue: Int, val nozzleId: Int, val userId: Int)
data class NewFormat(val shiftId: Int, val nozzleValue: Int, val userId: Int)

fun main() {

    val old = listOf(
            OldFormat(0, 10, 10, 0),
            OldFormat(0, 120, 10, 1),
            OldFormat(1, 11, 8, 10),
            OldFormat(0, 10, 1, 1),
            OldFormat(1, 50, 10, 10)
    ) // Example data

    old.groupBy {
        it.shiftId to it.userId // After it we have Map<Key, List<OldFormat>>, where key is pair of shiftId and userId
    }.map { entry ->
        val max = entry.value.maxBy { it.nozzleValue }?.nozzleValue ?: 0
        val min = entry.value.minBy { it.nozzleValue }?.nozzleValue ?: 0

        entry.key to (max - min) // Just do whatever you want with that data
    }.map {
        NewFormat(
                shiftId = it.first.first,
                userId = it.first.second,
                nozzleValue = it.second
        ) // And now map it into type you want
    }.let {
        println(it) // Just for seeing result
    }
}

Kotlin：groupBy并转换为其他对象

1 个答案: