無法在嵌套串列Kotlin中找到所有匹配值

嘿，我有串列，我想找到所有匹配的專案。我嘗試了一些代碼，但它不能用于所有查找專案。我需要以有效的方式做。我猜我下面的代碼回傳第一個匹配項。

團體

data class Group(
    val key: Int,
    val value: MutableList<GroupValue?>
)

組值

data class GroupValue(
    val isRead: Boolean? = null,
    val id: String? = null
)

主檔案

fun main() {
    val value = listOf(
        Group(0, mutableListOf(GroupValue(true, "1"))),
        Group(1, mutableListOf(GroupValue(true, "2"))),
        Group(2, mutableListOf(GroupValue(false, "3"))),
        Group(3, mutableListOf(GroupValue(true, "4"))),
        Group(4, mutableListOf(GroupValue(false, "5"))),
        Group(5, mutableListOf(GroupValue(true, "6"))),
        Group(6, mutableListOf(GroupValue(true, "7"), GroupValue(false, "8"))),
        Group(7, mutableListOf(GroupValue(true, "9"), GroupValue(false, "10"))),
        Group(8, mutableListOf(GroupValue(false, "11"), GroupValue(false, "12"), GroupValue(false, "13"))),
        Group(9, mutableListOf(GroupValue(false, "14"), GroupValue(true, "15"))),
        Group(10, mutableListOf(GroupValue(true, "16")))
    )

    val list = value.slice(2..9)
    var groupValue: GroupValue? = null
    list.forEach { messageGroup ->
        groupValue = messageGroup.value.find { it?.isRead == false }
        if (groupValue != null) {
            println(groupValue)
        }
    }
}

通過上面的代碼輸出

GroupValue(isRead=false, id=3)
GroupValue(isRead=false, id=5)
GroupValue(isRead=false, id=8)
GroupValue(isRead=false, id=10)
GroupValue(isRead=false, id=11)
GroupValue(isRead=false, id=14)

預期輸出

GroupValue(isRead=false, id=3)
GroupValue(isRead=false, id=5)
GroupValue(isRead=false, id=8)
GroupValue(isRead=false, id=10)
GroupValue(isRead=false, id=11)
GroupValue(isRead=false, id=12)
GroupValue(isRead=false, id=13)
GroupValue(isRead=false, id=14)

uj5u.com熱心網友回復：

您需要使用filter()代替find()（find()讓您只獲得一個物件，但您需要多個），如下所示：

fun main() {
    val value = listOf(
        Group(0, mutableListOf(GroupValue(true, "1"))),
        Group(1, mutableListOf(GroupValue(true, "2"))),
        Group(2, mutableListOf(GroupValue(false, "3"))),
        Group(3, mutableListOf(GroupValue(true, "4"))),
        Group(4, mutableListOf(GroupValue(false, "5"))),
        Group(5, mutableListOf(GroupValue(true, "6"))),
        Group(6, mutableListOf(GroupValue(true, "7"), GroupValue(false, "8"))),
        Group(7, mutableListOf(GroupValue(true, "9"), GroupValue(false, "10"))),
        Group(8, mutableListOf(GroupValue(false, "11"), GroupValue(false, "12"), GroupValue(false, "13"))),
        Group(9, mutableListOf(GroupValue(false, "14"), GroupValue(true, "15"))),
        Group(10, mutableListOf(GroupValue(true, "16")))
    )

    val list = value.slice(2..9)
    list.forEach { messageGroup ->
        val groupValues = messageGroup.value.filter { it?.isRead == false }
        if (groupValues.isNotEmpty()) {
            println(groupValues)
        }
    }
}

這將為您提供以下輸出：

[GroupValue(isRead=false, id=3)]
[GroupValue(isRead=false, id=5)]
[GroupValue(isRead=false, id=8)]
[GroupValue(isRead=false, id=10)]
[GroupValue(isRead=false, id=11), GroupValue(isRead=false, id=12), GroupValue(isRead=false, id=13)]
[GroupValue(isRead=false, id=14)]

為了獲得您想要的東西，您需要對代碼進行更多更改以將每個Group物件映射到一個串列，GroupValue然后將串列串列展平。檢查以下代碼：

fun main() {
    val value = listOf(
        Group(0, mutableListOf(GroupValue(true, "1"))),
        Group(1, mutableListOf(GroupValue(true, "2"))),
        Group(2, mutableListOf(GroupValue(false, "3"))),
        Group(3, mutableListOf(GroupValue(true, "4"))),
        Group(4, mutableListOf(GroupValue(false, "5"))),
        Group(5, mutableListOf(GroupValue(true, "6"))),
        Group(6, mutableListOf(GroupValue(true, "7"), GroupValue(false, "8"))),
        Group(7, mutableListOf(GroupValue(true, "9"), GroupValue(false, "10"))),
        Group(8, mutableListOf(GroupValue(false, "11"), GroupValue(false, "12"), GroupValue(false, "13"))),
        Group(9, mutableListOf(GroupValue(false, "14"), GroupValue(true, "15"))),
        Group(10, mutableListOf(GroupValue(true, "16")))
    )

    val list = value.slice(2..9)
    list.map { messageGroup -> messageGroup.value.filter { it?.isRead == false } }
        .flatten()
        .forEach { println(it) }
}

標籤：科特林

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