Kotlin 集合和对象总和

Question

我有以下课程：

class UserData(
        val firstSale: Date,
        val lastSale: Date,
        val ptuCodesList: List<ItemSale>,
        val taxList: List<ItemSale>,
        val salesList: List<ItemSale>,
        val taxTotal: Long,
        val saleTotal: Long,
        val currency: String = DEAFULT_CURRENCY,
        val canceledOrderCount: Int,
        val canceledSaleTotal: Long,
)

和模型类：

class ItemSale(
       val itemDescription: String,
       val itemsTotalValue: Long
)

我正在从我的数据库中获取我所有的 UserData 对象

dbRepository.getAllUsersData(): List<UserData>

现在我不知道如何对这个 List UserData 对象求和并作为单个对象返回，我的意思是，我不知道如何对包含在 UserData 对象中的那些列表 taxList/saleList 求和。在这些列表中，我需要对 itemsTotalValue 求和。

例子：

我们有两个 UserData 对象的列表：

class UserData(
        val firstSale: 238402384092L,
        val lastSale: 893231117482L,
        val ptuCodesList: List<ItemSale>,
        val taxList: List<ItemSale>, -> ("first", 4), ("second", 4)
        val salesList: List<ItemSale>, -> ("third", 5), ("fourth", 3)
        val taxTotal: 500,
        val saleTotal: 600,
        val currency: String = DEAFULT_CURRENCY,
        val canceledOrderCount: 3,
        val canceledSaleTotal: 4500
)

class UserData(
        val firstSale: 338402384092L,
        val lastSale: 9934798237482L,
        val ptuCodesList: List<ItemSale>,
        val taxList: List<ItemSale>, -> ("first", 7), ("second", 8)
        val salesList: List<ItemSale>, -> ("third", 1), ("fourth", 2)
        val taxTotal: 250,
        val saleTotal: 400,
        val currency: String = DEAFULT_CURRENCY,
        val canceledOrderCount: 4,
        val canceledSaleTotal: 400
)

结果：

class UserData(
        val firstSale: 238402384092L,
        val lastSale: 9934798237482L,
        val ptuCodesList: List<ItemSale>, //Stay same for all objects
        val taxList: List<ItemSale>, // ("first", 11), ("second", 12)
        val salesList: List<ItemSale>, // ("third", 6), ("fourth", 5)
        val taxTotal: 750,
        val saleTotal: 1000,
        val currency: String = DEAFULT_CURRENCY, // Stay for all same
        val canceledOrderCount: 7,
        val canceledSaleTotal: 4900
)

谢谢

Answer 1

目前还不清楚当“求和”两个具有不同 firstSale、lastSale 或 currency 的 UserData 时您希望发生什么。无论如何，我会编写一个将两个 UserData 加在一起的函数，以您想要的方式处理这些情况，例如：

fun List<ItemSale>.aggregateWith(other: List<ItemSale>): List<ItemSale> {
    return (this + other).groupBy(ItemSale::itemDescription)
        .entries
        .map { ItemSale(it.key, it.value.map(ItemSale::itemsTotalValue).sum() )}
}

data class UserData(
    val firstSale: Date,
    val lastSale: Date,
    val ptuCodesList: List<ItemSale>,
    val taxList: List<ItemSale>,
    val salesList: List<ItemSale>,
    val taxTotal: Long,
    val saleTotal: Long,
    val currency: String,
    val canceledOrderCount: Int,
    val canceledSaleTotal: Long,
) {
    operator fun plus(other: UserData): UserData {
        if (other.firstSale != firstSale || other.lastSale != lastSale || other.currency != currency) {
            error("Cannot add mismatched UserData $this to $other.")
        }
        return copy(
            ptuCodesList = ptuCodesList.aggregateWith(other.ptuCodesList),
            taxList = taxList.aggregateWith(other.taxList),
            salesList = salesList.aggregateWith(other.salesList),
            taxTotal = taxTotal + other.taxTotal,
            saleTotal = saleTotal + other.saleTotal,
            canceledOrderCount = canceledOrderCount + other.canceledOrderCount,
            canceledSaleTotal = canceledSaleTotal + other.canceledSaleTotal
        )
    }
}

那么你就可以reduce列表来获取你想要的：

fun List<UserData>.aggregate(): UserData = reduce(UserData::plus)

Answer 2

可能是这样的：

  listOfUserData.map{ it.salesList.map{ it.itemsTotalValue }.sum() }.sum()

一个简化但完整的例子：

class UserData(val salesList: List<ItemSale>, val taxList: List<ItemSale>)

class ItemSale(
   val itemDescription: String,
   val itemsTotalValue: Long
)

fun main() {

    val itemSale1 = ItemSale("A", 12) 
    val itemSale2 = ItemSale("B", 30) 
    val itemSale3 = ItemSale("C", 45) 
    val itemSale4 = ItemSale("D", 55)
    val itemSale5 = ItemSale("E", 23)
    val itemSale6 = ItemSale("F",  2)

    val listOfUserData = listOf(UserData(listOf(itemSale1, itemSale2), 
                                         listOf(itemSale5)),
                                UserData(listOf(itemSale3, itemSale4), 
                                         listOf(itemSale6)) )

    val sumSales = listOfUserData.map{ it.salesList.map{ it.itemsTotalValue }.sum() }.sum()
    val sumTax   = listOfUserData.map{ it.taxList.map{ it.itemsTotalValue }.sum() }.sum() 

    val sum      = listOfUserData.map{ it.salesList.map{ it.itemsTotalValue }.sum() }.sum() + 
                   listOfUserData.map{ it.taxList.map{ it.itemsTotalValue }.sum() }.sum()       


    println(sumSales)   // 142
    println(sumTax)     //  25 
    println(sum)        // 167

 }

合并对象的更新：

 val itemSale1 = ItemSale("A", 12)
 val itemSale2 = ItemSale("B", 30)
 val itemSale3 = ItemSale("C", 45)
 val itemSale4 = ItemSale("D", 55)
 val itemSale5 = ItemSale("A", 13)
 val itemSale6 = ItemSale("B", 29)
 val itemSale7 = ItemSale("C", 32)
 val itemSale8 = ItemSale("D", 21)

 val myMap = mutableMapOf<String, Long>()

 val listOfUserData = listOf(UserData(listOf(itemSale1, itemSale2),
                                      listOf(itemSale3, itemSale4)),
                             UserData(listOf(itemSale5, itemSale6),
                                      listOf(itemSale7, itemSale8)) )

 listOfUserData.map{ it.salesList.map{ myMap[it.itemDescription] = myMap.getOrDefault(it.itemDescription, 0L) + it.itemsTotalValue }}

 println(myMap)   // {A=25, B=59}

科特林游乐场

https://pl.kotl.in/aiGawyaJQ

Answer 3

您可以使用sumByDouble

class UserData(
    val firstSale: Date,
    val lastSale: Date,
    val ptuCodesList: List<ItemSale>,
    val taxList: List<ItemSale>,
    val salesList: List<ItemSale>,
    val taxTotal: Long,
    val saleTotal: Long,
    val currency: String = DEAFULT_CURRENCY,
    val resignOrderCount: Int,
    val canceledSaleTotal: Long,
    val fiscalEventsCount: Int,
    val nonFiscalPrintoutsCount: Int
){
    val sumOfTaxAndSales: Long
      get() = taxList.sumByDouble { it.itemsTotalValue.toDouble() }.toLong() + salesList.sumByDouble { it.itemsTotalValue.toDouble() }.toLong()
}

Answer 4

如果你想保持 Long 作为你的求和结果，你可以使用 map 函数。例如：

val taxListSum = taxList.map { it.itemsTotalValue }.sum()

我建议这样做，因为到目前为止 Kotlin 只提供 sumBy（它返回一个 Int）和 sumByDouble 来对集合的具体属性求和。