从lambdas或Kotlin返回:此处不允许“返回" [英] Return from lambdas or Kotlin: 'return' is not allowed here

问题描述

我正在尝试编写一个函数，该函数将告诉我字符串是不错的，好的意思是字符串在字符串中至少有一个字母重复.但是我无法从lambda进行返回，尽管if语句中的条件通过了，但它总是返回false.有人可以解释一下我如何赚钱吗?

I am trying to write function which will tell me that string is nice, nice means string has at least one repetition of letters in the string. But I can't to make return from lambda, it's always return false, though condition in if statement passed. Can somebody explain me how make return?

我试图写回信，但IDEA给了我消息科特琳:这里不允许'回信'

I have tried to write return, but IDEA gave me the message Kotlin: 'return' is not allowed here

fun main(args: Array<String>) {
    println("sddfsdf".isNice())
}

fun String.isNice(): Boolean {
    val hasRepeat = {
        for (i in 0 .. (length - 2)) {
            if (subSequence(i, i + 2).toSet().size == 1) {
                true
                println(subSequence(i, i + 2))
            }
        }
        false
    }

    return hasRepeat()
}

输出是:

dd
false

推荐答案

您可以标记lambda，然后使用标记的return:

You can label lambda and then use labeled return:

fun String.isNice(): Boolean {
    val hasRepeat = hasRepeat@ {
        for (i in 0 .. (length - 2)) {
            if (subSequence(i, i + 2).toSet().size == 1) {
                return@hasRepeat true
                println(subSequence(i, i + 2)) // <-- note that this line is unreachable
            }
        }
        false
    }

    return hasRepeat()
}

或者，如果不需要hasRepeat作为函数引用，则可以使用命名的本地函数:

or you can use named local function, if you do not need hasRepeat to be function reference:

fun String.isNice(): Boolean {
    fun hasRepeat(): Boolean {
        for (i in 0 .. (length - 2)) {
            if (subSequence(i, i + 2).toSet().size == 1) {
                return true
            }
        }
        return false
    }

    return hasRepeat()
}

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