Kotlin代码重构

Question

我有一个函数，它检查是否有搜索条件。

var currentStatus = MutableLiveData<List<Int>>()

private var sellerIds: List<Int>? = null
private var subSellerIds: List<Int>? = null
private var partnerIds: List<Int>? = null
private var productTypeIds: List<Int>? = null
private var brunchIds: List<Int>? = null
private var contractDateFrom: String? = null
private var contractDateTo: String? = null
private var completeDateFrom: String? = null
private var completeDateTo: String? = null

private var totalStatusCnt: Int = 10

val isSearching = ObservableField<Boolean>(false)

private fun checkIfSearchConditions() {
    if (currentStatus.value != null && currentStatus.value!!.isNotEmpty() &&
            currentStatus.value?.size != totalStatusCnt) {
        isSearching.set(true)
    } else if (keyword != null && keyword!!.isNotEmpty()) {
        isSearching.set(true)
    } else if (sellerIds != null && sellerIds!!.isNotEmpty()) {
        isSearching.set(true)
    } else if (subSellerIds != null && subSellerIds!!.isNotEmpty()) {
        isSearching.set(true)
    } else if (partnerIds != null && partnerIds!!.isNotEmpty()) {
        isSearching.set(true)
    } else if (productTypeIds != null && productTypeIds!!.isNotEmpty()) {
        isSearching.set(true)
    } else if (brunchIds != null && brunchIds!!.isNotEmpty()) {
        isSearching.set(true)
    } else if (contractDateFrom != null && contractDateFrom!!.isNotEmpty()) {
        isSearching.set(true)
    } else if (contractDateTo != null && contractDateTo!!.isNotEmpty()) {
        isSearching.set(true)
    } else if (completeDateFrom != null && completeDateFrom!!.isNotEmpty()) {
        isSearching.set(true)
    } else if (completeDateTo != null && completeDateTo!!.isNotEmpty()) {
        isSearching.set(true)
    } else {
        isSearching.set(false)
    }
}

而且checkIfSearchConditions方法看起来很脏，所以我想重构这个方法来说明清楚。

我试着做一个空的检查方法，

private fun checkIfNotEmpty(field: Any?): Boolean {
    return field != null && field!!.isNotEmpty() // isNotEmpty is not unsolved reference
}

但文件类型可以是列表吗？或者字符串？，因此获取'isNotEmpty‘不是未解决的引用’错误。

如何重构该方法以明确说明？

Answer 1

为List<*>?和String?创建两个单独的重载方法

private fun checkIfNotEmpty(field: String?): Boolean {
    return field != null && field.isNotEmpty()
}
private fun checkIfNotEmpty(field: List<*>?): Boolean {
    return field != null && field.isNotEmpty()
}

注意，在这些方法中，您不需要在!!中使用field!!.isNotEmpty()：因为它不是一个var，在检查它不等于null之后，Kotlin知道它不能变成一个var。

另一种更糟的方法是将Any?保持为参数类型，并检查运行时是否有List或String：

private fun checkIfNotEmpty(field: Any?): Boolean {
    return when(field) {
        null -> false
        is List<*> -> field.isNotEmpty()
        is String -> field.isNotEmpty()
        else -> false
    }
}

此外，所有具有相同主体的else if分支都可以使用||进行组合：

if ((checkIfNotEmpty(currentStatus) &&
        currentStatus?.value?.size != totalStatusCnt) ||
    checkIfNotEmpty(keyword) ||
    checkIfNotEmpty(sellerIds) || ...
) {
    isSearching.set(true)
} else {
    isSearching.set(false)
}

它可以改进得更好

val isSearchingValue = (checkIfNotEmpty(currentStatus) &&
        currentStatus?.value?.size != totalStatusCnt) ||
    checkIfNotEmpty(keyword) ||
    checkIfNotEmpty(sellerIds) || ...
isSearching.set(isSearchingValue)

Answer 2

Kotlin stdlib包含函数

public inline fun CharSequence?.isNullOrEmpty(): Boolean = this == null || this.length == 0
public inline fun CharSequence?.isNullOrBlank(): Boolean = this == null || this.isBlank()

您可以为Collection?定义类似的乐趣