dictionary - 由于 `HashMap.getOrDefault()` 函数中的接收器类型不匹配，以下候选均不适用

Question

根据Oracle官方文档，该HashMap.getOrDefault(Object Key, V defaultValue)函数可以带两个参数，但是当我运行以下程序时编译器报错。

fun main(args: Array<String>) {
    val numbersMap = mapOf(
        "one" to 1, 
        "two" to 2, 
        "three" to 3,
        "four" to 4,
        "five" to 5
    )
    println(numbersMap.get("one"))
    println(numbersMap["one"])
    println(numbersMap.getOrDefault("four", 10))
    println(numbersMap["five"])
}

---

C:\Users\forestfh\Documents\KotlinProjects>kotlinc GetOrDefault.kt
GetOrDefault.kt:11:24: error: unresolved reference. None of the following candid
ates is applicable because of receiver type mismatch:
public inline fun <R, T : String> Result<String>.getOrDefault(defaultValue: Stri
ng): String defined in kotlin
    println(numbersMap.getOrDefault("four", 10))

标签： dictionarykotlinhashmap

Answer 1

您可以使用getOrElse()扩展函数来检索存储值或默认值：

println(numbersMap.getOrElse("four") { 10 })